Merlin Cycles gave me the best info that they can send the forks to an RS tech centre to have v brake lower legs swapped with the normal disc only lowers. However with all the costs involved plus the forks even if a lower end SID you'd still be looking at £500+ .... I'm sure there will be someone that may say different but thats what I found relatively easily.
Also found a far east company that could get them for just over £300 delivered but wait was up to 2 months (plus you can prob add duty & VAT to that price once they land in the UK).
In the end I've settled for a set of 2012 model Mugura Menjas. Readily available, V & disc mounts, 85mm travel and a little over £300 so will see how they compare to the SID's on one of my other bikes.
Cheers.
Alex.