If you can get hold of a brand new head then that is the best starting point, when i had my engine built i bought a new one, it was then machined to grp A spec, i didn't want to spend the money on the work to be done and then find the head would be scrap if it needed one skim at any point in the future. Next best option is to source a 2nd hand head that hasn't been skimmed ever.
You really should speak to Karl 1st though about the welding and refinishing, as a new head is about £1000 - £1500 + VAT!