Im confused. You ask if you can keep the existing BB but then say you are changing the BB to a hollow tech.
Personally, I'd go for a Sora crankset then, you won't feel any improvement with something more fancy IMHO ~ these should come out at about £55 brand new, plus £11 for your BB and your done (you'll need to either buy or borrow a hollowtech BB tool, as its different to the one you have ordered to remove your FSA one, but they can be had for £15 or so). Looking at that frame, it will almost certainly be a BSA bottom bracket shell, by the way.Hope that helps.http://www.tweekscycles.com/Product.do?method=view&n=3518&g=781386&p=300917&d=124&c=4&l=2&utm_source=Google&utm_medium=Base&utm_campaign=Road%20Chainsets%20&%20Cranks&gclid=CKSsrpmps8wCFeUV0wod5LgBZQ
Any particular reason you want to swap front rings or are you just doing it for the hell of it and have money burning holes in yer pockets? There won't be much difference in performance between the Sora and FSA front rings. Just cosmetic. I've same set on my Giant. When I upgrade I'll go 105 throughout to get the extra 2 gears on the back to keep the spacing between a little smaller.
I've seen a 105 set for about, £65. Don't mind paying that. I gather the 105 is a 10 speed, Vs the 9 speed of the Sora. Having read up a little it would seem I'll be ok with that as long as a 9spd chain is used?