Ran this by Stef at WOS did one last test which was to try the box on someone else's sat dish and the box worked perfectly and the problem has ended up looking like it is my LNB.
So i'm happy with that and jsut thought id post back here in case anyone else gets a similar problem.

Strange thing is though the dish/lnb worked perfectly with the old box so maybe just some sort of partial incompatibility, ahh well who cares a universal LNB is only around £10 and easy to change so that'll do me.
..... unless I can squirrel some cash away from the wife, order me a motorised dish from the sponsor then fit it while she's out
hehe knowing me though id go flying n fall off the ladder trying to rush