Hi Jocelyn,
I'm going to be slightly pre-emptive into what kinda place you'll end up with from what you've said and the housing allowance amount you have, here's what I'd estimate >
Council tax - this is the tax paid for local services and amenities that everyone contributes to throughout the country. Nearest equivalence in the USA would be 'property taxes' - and of course, it's mandatory.
http://www.slough.gov.uk/services/1286.aspthat's the ratings for the current year and pricing levels for the tax.
If you're going to be renting a 4 bed house in a 'nice' area, with considerations of it being safe, secure and family orientated then pretty much all of the houses will be worth quite a bit more than £320,000 and as such would put you in the top bracket for council tax. You'll pay the full amount (no single persons 25% discount) and that comes out to be about £192 per month.
Other posters may know for sure, but I don't know of any releifs or breaks from the council tax for someone in your situation - maybe find out from the council themselves or other's here may know more.
without wanting to pour cold water on your housing plans, please factor in all the associated 'extra' costs of renting a house. The usual utilities - heating and electric costs will be quite substantial for a 4bd house. Water rates will be substantial too.
Then add on the maintenence costs you as a tennant need to fulfill during your time there, it's not as much as if it was your own home of course, but should be factored into your monthly budget nevertheless.
The remaining costs are really up to you and what you'd like for your lifestyle. Sky Telly, telephones, better appliances than given by the landlord, specfic requirements you may have etc will all add into your budget for the house.
All that said, looking at rightmove.co.uk there's not many 'furnished' places listed and of those that are, theres a couple in Langley at £1500pcm and then it rises quickly to £1650 then 1800 then £2000 pcm - and some of those houses I know exactly where they are as I often drive near them! (they're really nice though!) have a look at rightmove.co.uk, search for 'slough' and '3 miles around this area' and 4bds and furnished and max 2000 per month. Repeat the same for maidenhead, ascot and other places mentioned by other posters too.
I along with AnneR will gladly forward you copies of local papers with property listings no problem at all just in case you can't find 'property news' in any of the local estate agent branches.
Good luck!
DtM! West London & Slough UK!