Hi there,
My husband and I live in the Southeast in a large town called Reading. Its very close to London (about 30 miles west) and very expensive. You also have to consider counsul tax where ever you buy or rent (like property tax in the states, note the renter pays it here)....we pay £108 per month on top of our rent which is £800 for an extremely small 1.5 bedroom house.
£25,000 will give you roughly £1500 net income per month. Needless to say.....its very expensive over here, especially in London or towns close to. Another key thing to remember is a £ pretty much equals a $. If you go to Pier One or Home Base (i.e. - Home Depot) for example things will cost the same as in the US....the difference....you aren't bringing home the same type of salary in the US. Salaries tend to be 1/3 to 1/2 lower over here.
Julie
I agree with Julie. If you equate the £ to the $ as she has stated, then you can gain a better picture of what your salary will get you. I am sure that an average breakdown of the cost of everyday items can be gained as well as your research into housing costs. For example, gas tends to be a lot more expensive here, but bread I find cheaper. When weighing it all up and deciding what figure has to be there for you, it might be worth it to factor everyday things in as well--might be too complicated, but it's better to know than to find out that you did not ask for enough.
As someone stated above, there are plenty of volunteer opportunities if working is not an option b/c of visa issues with your wife. I am sure that she can meet lots of friends through here and gain more through volunteering to keep her busy.
I have visited Edinburgh once and loved it. I have visited London many times and have NEVER come away saying that I loved it. I think as Graham suggested, it would be a great idea to take a trip here and visit for yourself. I don't know if it's possible to take off the holiday goggles while here, but maybe all of your research may help with that.

Welcome to the site.
Jenninberks