I am guessing here, but the labor charge for a head gasket is around five hours, plus parts. The gasket set is as Colin notes. In the US, the FelPro brand gasket is vastly preferred because of quality. You will also want the head to be cleaned,a checked, and rebuilt with new stem oil seals and rubber valve tappet washers. That will cost the sterling equivalent of about $150. You might have complications due to warped or cracked head, broken exhaust studs, or faulty valves, all of which would be extra cost.