French Connection is more of a Main Street brand so it's a bit unfair to say it's a designer store for 'minted punters' a term I really find annoying especially 'punters' when 'passengers' are concerned.
If you don't want to shop you don't need to as you could always have a coffee and admire the marvellous views from the large glass windows overlooking the whole airport!
Terminal 5 is a great terminal it has lots to offer to all tastes 'minted or not' and I always enjoy using it, it makes a huge difference after a flight with BA from Terminal 3.