Had a quick look at Cambridgeshire with 8 seats whilst I was playing around with another project. As an additional constraint, I tried to keep all the seats within 5% +/- of the county average, though due to the ward sizes that doesn't cause many problems.
554,887 electors, meaning with 8 seats you've got an average seat size of 69,361. Four of the authorities concerned have had new boundaries since the last review started and Cambridge will have when the next set of elections come round, but in most cases that's not a huge impact.
With a 5% deviation, both
Peterborough (70,623) and
Cambridge (67,266) can stay as they are. Alternatively Cambridge could gain Queen Edith's and become co-extensive with the city, but given that the December electorate is a clear undercount of the normal general election electorate I think it's best to leave it as is.
All the other current seats have over 80,000 electors (in the case of NW Cambs, nearly 90k) so need to shrink. Fenland district is the right size for a seat (69,361), so the main question there is whether you keep calling it
NE Cambs or rename it after the district. With the other five seats, there are two main options: one is the least change option, crossing fewest local authority boundaries, the other is the prettier options which works best on the ground but is more disruptive.
In both of those options,
NW Cambs keeps all its bits of Peterborough, but only five wards of Huntingdonshire in the north and west of the district.
In the least change option,
Huntingdon (69,201) loses St Ives but gains Upwood & The Raveleys, whilst
SE Cambs (71,566) gains the rest of East Cambs and loses all its portions of South Cambs DC west of the Cam.
S Cambs (67,560) grabs Linton from SE Cambs, but in the north of the seat pulls back south of the A14.
Mid Cambs (72,098) combines Cambridge suburbs north of the A14 with St Ives and Ramsey, in a classically incoherent leftovers seat. In total, 90,608 electors are moved into a new seat.
The prettier option was something I found by accident, when I was trying to make the 8th seat by moving St Neots out of Huntingdon instead. I kept constructing awkward boundaries around Cambridge until I realised that I was prioritising local authority boundaries over local links. In actual fact, north of Cambridge the Cam and the Ouse are reasonably effective boundaries, with only a few bridges between Cambridge and Ely. If you use the rivers rather than the local authorities as your guideposts, you get the following:
Peterborough,
NE Cambs,
Cambridge and
NW Cambs as above.
Ely (70,811) is the successor to SE Cambs, with a bare majority of electors from the old seat (41,364 out of 82,557) having come from it. It's made up of the west of East Cambs DC, together with parts of South Cambs DC west of the Cam and north of the A14.
SE Cambs (67,188) is then narrowly the new seat - with 41,193 having come from the old SE Cambs and the balance from S Cambs.
SW Cambs (70,808) is made up of the remainder of S Cambs plus St Neots and hence reverts to its prior name.
Huntingdon (71,618) makes up for losing St Neots by adding 5 wards from NW Cambs.
This version moves 139,329 electors and crosses an additional local authority boundary, so on least-change grounds it's clearly inferior to the first option, but in terms of coherence I think it has a lot to be said for it.
