The problem with AM3+ is that all the mATX motherboards are based on old chipsets and old designs. The few 880G based AM3+ motherboards which have the SB850 southbridge are not cheap either and are hard to get.
The Biostar 970 motherboard has VRM cooling too,and at least AFAIK Biostar has made solid budget AMD motherboards. The Gigabyte one does not have this,although I suppose you could always add your own heatsinks at some point.
Looking at the postage situation,Ebuyer does free supersaver postage,Amazon does free postage and Dabs will charge a few quid for postage,and you get free games. You can get a HD7770 from Amazon or Ebuyer though,and this case might be an alternative to the Merc Alpha:
http://www.ebuyer.com/390898-casecom-cs-13-case-cs-13
I suppose you could get everything from Ebuyer instead,but you will get less for budget.