Road bike recommendations

Just get a CAAD10 with 105, or if you're feeling flush, Genesis Volare to match the fleet.

A racier bike will feel quicker, but the biggest difference is you, just work at it more, eat differently, core body strength etc. and you'll be surprise how much easier it is to climb on the 520 Genesis.

Didn't that have a steel fork instead of a carbon?

Yep, it's all steel. The other possible option is getting a carbon fork fitted (maybe Columbus Hiver so I can still run my guards), applying some HTFU and saving a lot of money.

I'm 6ft and 10.5 stone, and already look "too skinny" according to my GF so I'm not sure there is much more weight to lose :). Core strength (do you even) is another issue though!