You need to find out how much you can borrow from a bank/building society BEFORE you find a house. Lenders have limits on how much they will lend you either based on affordability models or salary and will look at any loans, credit cards and deposit you may have.
Go to an INDEPENDENT Mortgage Broker rather than direct to a bank or building society. Being independent should mean that they can look at the whole of the market to find the best mortgage deal for you. This is important as all the lenders set their own criterias as to how much they will lend and to whom so although one may not be able to do what you want there may be many others that will. The independent adviser will also be able to find you the best deal for your individual circumstances. Most Estate Agency based advisers work from a panel of lenders so be prepared to ask them whether they look at the whole of the market or just a cross section.
When it comes to the costs involved, the mortgage lender normally charges an arrangement or booking fee which can often be added to the mortgage (this does mean that you will incur interest on it though) and also a valuation fee to check that the property is suitable security for the mortgage. You will also have solictor fees including stamp duty and it is worth getting an estimate from a couple of solicitors. It is worth trying to find one that offers no sale, no fee which means that if your purchase falls through you do not get charged for their services just any expenses they have paid out on your behalf. The mortgage/financial adviser may charge you a fee but should tell you upfront at the first appointment. You should not be charged for the initial chat with them. I charge just £50 once an application is submitted to cover administration time as most mortgages take 6 - 10 hours worth of admin time but others charge up to 2% of the mortgage so worth shopping around again.
Hope this gives you a clearer idea of everything and good luck!
Years of experience as an Independent Financial Adviser