I did one of the GOS girls in March, got the technique a bit wrong and had no results. three weeks later, try again, she's in pig and due on 4th August! Will let you know the results.
We use Deerpark pedigree pigs based in Northern Ireland (do a google), i believe it's the only place you can get pedigree rare-breed semen from in the UK, and is supported by the RBST. Very effecient service, costs about £26 for three pots of the 'magic pig potion' as my son calls it. Probably cheaper than using a boar without the associated move standstills and transport headaches.