Boundary review summary: South West

Bristol
Only one ward needed to be reallocated in the whole of Bristol to create four constituencies of the right size: one ward has switched from Bristol West to Bristol East that doesn't alter the political balance in the city at all.

Cornwall and Devon
A lot of the media seem, not unreasonably, to have used the pairing of Cornwall and Devon to illustrate the fact that county boundaries are being crossed for the first time. The new seat that cross the Tamar does so in the north of the county taking the Torridge out of Torridge and West Devon. This seat is notionally Lib Dem but it could easily go Conservative.

The consequence of Cornwall losing half a seat is to recreate the Falmouth and Camborne constituency, which is of course the only seat in the county Labour has ever had the remotest chance of winning. The party's vote has declined significantly since it was a Labour seat from 1997 to 2005 and we'd still start a distant third in this new version; but Jude Robinson's big council gain shows there are votes at the Camborne/Redruth end of the seat, and the return of Falmouth is a big help - provided Labour is successful in amking the case that it is a better depository for anti-Tory votes than the Lib Dems here.

Elsewhere in Devon, Exeter remains unchanged, but Plymouth undergoes some considerable change. Plymouth Moorview regains Devonport and with it that historical seat name; it loses some more Conservative areas to the east and Labour becomes stronger here.

But the marginal seat that is essentially Plymouth Drake is destroyed and Plymouth Sutton makes a return. Sutton was controversial Tory minister Alan Clark's seat until it was abolished in 1997 and, containing affluent suburbs like Plymstock (though not Plympton, which goes in with Tavistock), it was the most strongly (though not overwhelmingly) Conservative. On these boundaries it might well take a national landslide win to see Labour succeed here.

Dorset and Wiltshire
Dorset, Wiltshire, Somerset and South Gloucestershire need to be paired to meet the new quota requirements; and while a Dorset/Somerset pairing was entirely possible, the Commission have chosen to twin Dorset with Wiltshire.

There is little of interest to Labour here: all three prospects: the two Swindon seats and South Dorset remain unchanged. But the changes are consequential for the Lib Dems.

Although the abolished seat is what used to be called Westbury and is now "South West Wiltshire", which was strongly Conservative, the ripple effects actually wipe out a Lib Dem MP: Annette Brooke in Mid Dorset and Poole North. Her seat loses some of the Poole bits and gains a chunk of Christchurch and a bigger chunk of North Dorset - both of which are solidly Tory. As a result, the Guardian estimates that her new seat: Blandford and Wimborne would have a Tory majority of nearly 5,000.

And on the other side of Westbury, after waiting decades for a winnable Chippenham seat to be created, Chippenham itself goes back into North Wiltshire and the geographic bulk of the constituency is renamed Trowbridge - both of which are notionally Conservative.

Gloucestershire

Gloucester loses a ward to Forest of Dean which doesn't really change the marginality of the county seat, though it does mean Forest of Dean crosses the Severn, somewhat unnaturally. Stroud and the other Gloucestershire constituencies haven't been touched.

Somerset

There are no Labour prospects in what the Boundary Commission calls Somerset (as distinct from North Somerset and North East Somerset which they treat as entirely distinct areas). Lib Dem prospects are boosted in Taunton and the old Somerton & Frome seat (now Glastonbury and Wincanton), but the encroachment of Wells towards Bridgwater notionally appears to flip that seat back to the Tories (presumably minus David Heathcoat-Amory).

North East Somerset is more interesting though, because Labour until 2005 held a seat called Wansdyke here, centred on Keynsham. That doesn't make a return, but by pairing this area with South Gloucestershire there is a new Kingswood and Keynsham seat which is marginal, but somewhat better for the Tories than the seat Chris Skidmore gained last year. The rest of North East Somerset merges with Frome and will presumably be where Jacob Rees-Mogg transfers; his opponent in this seat will be the Lib Dems but he'll start about 4,500 ahead.

The old Northavon seat grew to form, essentially, two new seats at the last election. Filton & Bradley Stoke went Tory in 2010 while Thornbury and Yate was held by Lib Dem Steve Webb. Those two have been broken up and merged anew; Yate now has its own seat which will be very, very marginal but is clearly the seat Webb will go for (assuming he stands again) while Thornbury and Filton will be slightly better for the Tories, but still competitive.