im a mechanic, Its highly likely that there would be some valve damage. You mite beable to buy a new head off ebay complete with valves and cams for £200 ish. u have to make sure u get the right one to the engine code. Valves cost between £5-£10 a valve. Then would need bedding in with grinding paste!!! Also if your taking head off then i would advise to get the head skimmed. thats cost bout £50. Head set bout £100 with head bolts. I reckon it would cost u bout £500 ish to have the latter done with labour.Cylinder leak test will tell u bout any bent valves
Head bolts are about a quid each or so. Head gasket set, about 30. 2nd hand head I would not spend much more than 50-60. The real cost comes if there is piston damage. £500 is far too much to spend.