What I can certainly see is a fragmented 2012 fundraiser, with certain
donors staying with WMUK and others switching to WMF because that's
where the default landing page now points them to. Lots of returning
donors will be very very confused either because they can't gift-aid
their donations, or because two "Wikipedia organisations" are asking
for their money at the same time.
The split has always been a problem, ever since WMUK Version 1.0 in my