PE to UC Upgrade

Hi all. Wondered if anyone could help with this one. I'm a VA flying club member as well as a FVC member. Booked a holiday to Jamaica next June through VH and upgraded to PE for £500 each return. I now have enough points on my VA red card to upgrade to UC but after 3 phonecalls backward and forwarded between VA and VH now seem to have ascertained that this is not possible. VH advised it was and said to ring VA. VA advised that booked in H class and therefore needed a qualifying fare ticket for them to upgrade and said that VH could do this. VH says that it would be prohibitively expensive for me to pay the additional sum to upgrade the class of the ticket - would have been cheaper to just buy a UC ticket rather than use my miles. Problem is that the price they are quoting me to upgrade from PE to UC through VH is an additional £700+ each for return. This would then take the total amount paid to upgrade from Economy to UC up to over £1300 each for the return journey. Having just checked on-line, I can get a standard Z class return ticket on exactly the same flight through VA for £1200+ and this does not include my 10% discount! How on earth can this be correct? Anyone any ideas? Should I challenge the PE to UC upgrade cost with VH? Does anyone know of any way I can use my miles for an upgrade on this fare? Thanks all.