G-CPTN is right, make sure that your mortgage company and your insurers are happy, you will almost certainly have to pay a higher mortgage rate, and most 'regular insurers' don't touch let properties.
You will also be liable to CGT, for the proportion of the gain attributable to the rental period, when you sell - subject to certain exceptions.
You will have to pay 40% on this unless you own it in joint names, in which case you will pay 40% on half and Mrs PA will pay at her marginal rate on half.
You don't have to make the first (lump sum) tax payment until the January following the end of the tax year that you start the let (so don't spend it all). So if you start in say, May 2012, you won't pay until Jan 2014. You then have to pay an estimated amount on account for future years.
You don't need to wade through a load of IR stuff, there are very clear leaflets they produce on all this, including what you can and can't claim for - I don't think you will be able to claim your married patch.
Having let since 1996, I wouldn't waste your money on a tax advisor. Don't listen to anything your letting agent says without checking. The contract is between you and the tenant. Filling in the annual tax forms is straightforward and well explained.