If I'm frank, wireless range extension isn't too good, and between different companies products? It's basically a recipe for bashing your head against the wall in desperation at how impossible/full of fail it is.
Though it'll require buying some new stuff, the best and easiest way to get what you want is likely to cut the Home Hub out of the equation entirely and to buy an Airport Express and a couple of powerline network plugs to make your network look like it does below.
Openreach VDSL modem --Ethernet--> Time Capsule --Ethernet--> First powerline plug
Then wherever the signal is both needed and terrible/nonexistent:
Second powerline plug somewhere else --Ethernet--> Airport Express
The powerline plugs use your existing wiring to essentially give you the advantages of having a wired connection without the annoyance of having to run new cable everywhere. The Airport Express can do wireless bridging, but the performance will be quite a bit lower and you'll not have the freedom to put it in a total connection blackspot.
Oh, and as a nice bonus, providing you make sure you plug the Ethernet cable for the Airport Express into its WAN port, in my experience Airport Utility quickly twigs exactly what you're trying to do and does pretty much all of the work for you, which is nice of it.
In terms of what powerline adapters to get, I was researching this recently and am pretty sure I'd go for a couple of Solwise NET-PL-500AV-PIGGY adapters:
http://www.broadbandbuyer.co.uk/Shop/Specifications.asp?ProductID=12622