Costs will obviously depend very much on where you are living.
If you don't have your own furniture then a furnished property is obviously quite tempting but do bear in mind you will be responsible for looking after the furniture as well as the property (i.e if you cause any damage you may have deductions from your deposit).
Unfinished properties will typically include the 3C (Curtains, Carpet/floor covering and Cooker) and then you can get your own furniture which obviously gives more choice in what you need to get and you don't have to worry about spillages quite as much.
Also consider that with a furnished property you will be stuck with whatever the landlord decides to put in there. If you need a particular type of bed for instance then you may not get on well with one the landlord supplies.
I've lived in both and have to say I prefer unfurnished as they are usually cheaper and I've acquired quite a bit of stuff over the years anyway.
If you are planning to eventually buy your own place then renting unfurnished and acquiring some basic furniture will mean you don't have to spend as much when you do eventually buy.
Council tax will depend on the property band. Ask the agent/landlord and then check out the charges on the local council website.
Gas, electric (and water with a meter) will depend on consumption. Some people can have a tendency to whack up the heating when nobody is looking so can cost a fair bit. I'd suggest it's not unreasonable to budget for £40 pcm each. The general rule of thumb it that if you have more bathrooms than people then a water meter will probably be cheaper. The converse is also true.
Phone/broadband/TV depend on what you want and who you get it from obviously. If you can get cable then Virgin have some very good deals.
You will also need to provide insurance for you possessions. The internet is your friend on this one. Budget about £20 pcm although you may need more cover if you have a lot of high value items. Accidental damage cover for the landlords possessions may also be a good idea (and may in fact be required by the letting agent).
If you are renting with tow other non-related adults then you may be a renting a HOMO (

, but seriously, a House of Multiple Occupancy). In which case the landlord has additional obligations to do with things life fire alarms and the general quality of the property. What the local council classes as a HOMO varies so you might want to check with the council and also make sure the landlord knows before you move in.
When looking at properties bear in mind that it is now compulsory for the landlord/agent to provide you with an energy performance certificate for the property (like you get in a Home Information Pack). Your deposit must also be protected in a government approved deposit protection scheme. If it isn't then the landlord is breaking the law.
You also need to budget for food obviously. Whether you and you prospective house-mates want to share the cooking or do your own thing can impact the cost. It's generally cheaper per head to make larger quantities to communal cooking can work out cheaper.
And finally, the
Shelter website has lots of useful information for tenants. Or if you want to know specific legal stuff then rented accommodation comes under department for Communities and Local Government -
clickey.