I have noted another by-election seat that changed hands on 06 May - South Cambridgeshire: Girton a Liberal Democrat gain from Independent. The posting below has been amended accordingly.There were 362 seats contested on 06 May (one was countermanded) with 104 (29%) changing hands. The results can be summarised by:
| Party | Defended | Retained | Gained | Lost | Won | retention rate |
| Conservative | 136 | 129 | 78 | 7 | 207 | 95% |
| Labour | 129 | 89 | 11 | 40 | 100 | 69% |
| Liberal Democrat | 39 | 21 | 7 | 18 | 28 | 54% |
| Green | 7 | 4 | 4 | 3 | 8 | 57% |
| UKIP | 1 |
|
| 1 |
| 0% |
| Localist | 17 | 6 | 1 | 11 | 7 | 35% |
| Independent | 31 | 8 | 3 | 23 | 11 | 26% |
| Plaid Cymru | 1 | 1 |
|
| 1 | 100% |
| SNP | 1 |
|
| 1 |
| 0% |
| Total | 362 | 258 | 104 | 104 | 362 | 71% |
Conservatives gained 35 seats from Labour, 18 from Liberal Democrats, 16 from Independents, 7 from Localists and 1 each from SNP and UKIP.
They lost 5 District Council seats, including 1 "double" election, 1 Unitary Authority "double" election and 1 County Council by-election subject to re-organisation:
* losing 2 seats to Labour
- Hertsmere: Borehamwood Kenilworth; 2 Labour / 1 Conservative 2019, Conservative gain February 2020 by-election, Labour take original Conservative seat
- Peterborough:Fletton & Woodston; 2 Conservative / 1 Labour 2016, Labour hold 2018, Conservative hold 2019, Conservative hold 2021 annual seat
* losing 3 seats to Liberal Democrats
- South Lakeland: Broughton & Coniston; 2 Conservative / 1 Liberal Democrat in 2018, Liberal Democrat gains in 2019 and now 2021 gives all 3 seats
- St Albans: Harpenden East; Conservatives win all elections 2007 to 2019, Liberal Democrats prior years and now both seats in 2021
- Wealden: Hailsham North; single member seat created in 2019
* losing 1 seat to Greens
- Cumbria: Ulverston West; newly elected County Councillor previously gained Ulverston West District ward in 2019
* and 1 to an Independent
- Maldon: Tollesbury; single member ward Conservative 2019, 2015 and 2011, Labour 2012 by-election, Independent 2007 and 2003
Labour lost 35 seats to the Conservatives, 3 to Greens and 2 to Liberal Democrats.
They gained 3 Metropolitan Council seats, 2 Unitary Authority "double" elections, 5 District Council seats and 1 in Wales
* gaining Hertsmere: Borehamwood Kenilworth and Peterborough: Fletton & Woodston from Conservatives
* gaining 1 seat from Greens
- Sunderland: Washington South; Green gains in 2019, regained in 2021 when Conservatives top poll to win first seat since 2008
* 6 seats from Independents
- Allerdale: St John's; 2 Independent / 1 Labour in 2019. Conservative close runner-up and gains slightly larger County Council seat
- East Staffordshire: Eaton Park; traditional Labour 2 member ward where Independent gained one seat in 2019
- Manchester: Clayton & Openshaw; 3 Labour 2018, Labour narrowly in 2019 but Independent gains in February 2020
- Rossendale: Stackstead; traditional Labour ward which Independent gained in 2019
- Southend-on-Sea: St Lukes; Independent ward since 2011 but Conservative now gains annual seat and Labour by-election seat
- Wakefield: Airedale & Ferry Fryston; traditional Labour seat won by Independent in 2019 with Labour now winning both seats
* and 2 seats from Localists
- Bolover Pinxton; traditional Labour 2 member ward won by Pinxton Independent in 2019
- Rhondda Cynon Taf: Penrhiwceiber; traditional Labour 2 member ward won by Cynon Valley Party in 2017
Liberal Democrats lost 18 seats all to the Conservatives
They gained 1 each London Borough, Metropolitan Borough and Unitary Authority seat along with 4 District Councils seat
* gaining the 3 seats of South Lakeland: Broughton & Coniston, St Albans: Harpenden East and Wealdon: Hailsham North from Conservatives
* gaining 2 seats from Labour
- Kirklees: Golcar; Labour in 2018, 2015, 2012, Liberal Democrat in 2019, 2016, 2014. Labour wins annual seat, Liberal Democrat by-election
- Luton: Round Green; 2 Labour / 1 Liberal Democrat 2019, 2 Labour / 1 Conservative 2015, 3 Labour 2011, 3 Liberal Democrat 2007 and 2003
* 1 seat from Greens
- Richmond: Hampton Wick; Conservative ward up to 2014. Liberal Democrat gains 2015 by-election and 2018 contrived 2 Liberal Democrat / 1 Green
*and 1 seat from an Independent
- South Cambridgeshire: Girton; 2 member seat electing in 2018 an Independent and Conservative
Greens lost 3 seats, 1 each to Labour, Liberal Democrats and a Localist
They gained 1 each in a Metropolitan Borough, Unitary Authority, District, District Council and a County Council by-election subject to re-organisation
* gaining 3 seats from Labour
- Brighton & Hove: Hollingdean & Stanmer; 2 Labour / 1 Green 2019, 3 Labour 2015, 2 Green / 1 Labour 2011, 3 Labour 2007 and 2003
- Knowsley: St Gabriel; previously very strong Labour ward where Greens won by-election seat using strap "save our green space" strap line
- Thanet: Central Harbour; 2 Labour / 1 Green 2019, 2 UKIP / 1 Labour 2015, 3 Labour 2011, 2 Labour / 1 Localist 2007, 3 Labour 2003
* as well as Cumbria: Ulverston West from the Conservatives
Localists lost 7 seats to Conservatives and 2 each to Labour and Independents
They gained 1 seat from Greens
- Rochford: Hullbridge where the former Green Councillor was now elected for Rochford District Residents
Independents lost 16 seats to Conservatives, 6 seats to Labour and 1 to Liberal Democrats
They gained 3 seats
* Allerdale: Aspatria from Putting Cumbria First - Conservative topped the poll in 2019 holding the second seat
* Tendring: Eastcliffe from Holland-on-Sea & Eastcliffe Matters, single member ward created in 2019, along with
* Maldon: Tollesbury from Conservatives
Both UKIP in Tendring: West Clacton & Jaywick Sands and SNP in Stirling: Forth & Endrick lost the only seat defended to the Conservatives.
