I'd also suggest the 8X magnification rather than the 10x for watching birds while dog walking/general use. As with a telephoto lens, the higher the magnification the more prone to 'shake' they become. Also 8x will usually give a wider field of view, which can make it easier to find the bird you've just spotted. I can't suggest any particular make or model for around the £100 mark as I've not bought in that price range, but searching for some reviews, tests and recommendations on some of the UK birdwatching forums might be worthwhile?
Binocular technology seems to have come on in leaps and bounds over the last 15 years, I wanted some new bins about 8 years ago and after reading several tests and reviews I chose the Hawk Frontier ED, and paid about £230 for them. They are still going strong and I couldn't believe how bright and clear they were compared to the £60 pair I had before, and how much better the 'depth of field' on the focus was too, which makes a difference when trying to quickly focus to ID a bird you've just spotted in a tree.
I compared the Frontier EDs against a friend's £1,500 Swarovski binoculars on one occasion, and image-wise in reasonably good light neither of us could see a big difference between them, certainly not what we'd have called a £1270 difference anyway! I'm sure the Swaros would have been better in low light/dusk and would last a lifetime, and if I used binoculars almost every day or relied on them professionally as an ornithologist, then I'd have gone for the Swarovski ones if my budget allowed, but it's horses for courses.
This goes to show there's some good value for money binoculars out there though, it's just a question of doing some research on the internet to find them. However, if it turns out that spending an extra £30 or so will nudge up into the next 'quality bracket', and the improvement in image quality is fairly noticeable, then I'd suggest your fiend gives it some serious thought if it won't break the bank, as the quality is usually appreciated long after the price is forgotten. Hope this is useful to you and anyone else in finding some bins to compare and choose from.
