Do you currently have a mortgage? If so, you shouldn't need a solicitor.
Many lenders will include a free legal package in their remortgage deals, which mean their chosen solicitor will cover the legal requirements.
I'd recommend using a broker to get the best deal; London and Country are a free service (by phone and email). We now use a face-to-face service (personal preference) and we paid a one-off fee of £200 for lifetime service. Worth it considering we have a long mortgage and are likely to remortgage every couple of years. He sorted out additional borrowing for us (for some home improvements) at our last remortgage.