This morning I spent a couple of hours in Banbury, trying phones, not being sold things and generally gathering data. Conclusions are thus:
The Motorola Razr i is a first class Android handset, being fast & smooth, feeling really nice in the hand, having a good screen, acceptable camera and brilliant battery life. The store demo model had been running for 1 day 18 hours and was down to 75%. Sure it wasn't being used hard, but that's real world *phone* usage. Downside is that this phone is that it's highly unlikely to ever get software updates, and it's still on Icecream Sandwich, which is a bit meh.
The Sony Experia T - on special offer with O2 - is a niceish phone, great screen, not too large, but can be laggy (I saw one example in carphone warehouse that was every bit as bad as my HTC Desire on a bad day). The camera was being pushed as the best available, but was unimpressive in store. It also has a reputation for poor battery life. Not a candidate, even at £16 a month.
Had a look at the Samsung SII, SIII and SIII Mini. The SIII and SII were both larger handsets than I wanted, with the SIII a 'Phablet'. The SIII Mini was the right size, but it's a budget spec phone at a mid-range price, and felt a bit nasty TBH, especially after the Razr and Sony.
Windows phones were tried and found to be good but flawed. The tile system is excellent and intuitive, handling great, animations beautiful and smooth. It's hard to over-emphasise how good the animations were, as they made every Android phone afterward seem gritty and jerky. I tried a couple, with the Nokia 820 being most likely candidate since it's neither excessively large nor too expensive. Some annoyances: certain applications insist on only operating with the phone horizontal and it's all a bit 'toys R us' looking at times. Biggest killer is the premium prices, especially for the 920, when they need to find ways to increase user base. If the 920's camera was in the 820 then I'd have been keen, even though the pricing was a little high. Battery life is also short on the 820. Sadly this is probably a no-go.
Surprise final entry - the iPhone 4S. I tried one, really not wanting to like it, and in some ways I don't. It's terribly Mac-like, and feels claustrophobic, restrictive in a what you see is all I will do, ever, desperately smug kind of way. Yet some aspects, like the iBook reader worked really well, and were much more impressive than, say, the Kobo app on my HTC. The camera was also noticeably good, the screen is very sharp and clear and, joy of joys, it's no bigger than my current phone and feels nice in the hand.
So it will likely come down to what deals I can get. Razr vs 4S. I've found a deal for the 4S at £25 month including phone, but recall seeing the Razr at quite a bit less. The 820 is STILL attractive, but probably won't fly. Personally I think WP8 is potentially a lot better as a phone OS than either Android or iOS, both being adaptations of traditional desktop interfaces, but I'm not willing to pay to help see it developed further.