With a sensible regulatory structure putting GPS Overlay approaches in place would make sense
1 - Over time you could phase out the DMEs (maybe very interesting if OFCOM has their way)
2 - You create a framework to introduce LPV approaches in the near future - saving the megabucks for an ILS in places like Oxford and Lydd that have just sprung for all of the ground based radio kit (you would still need to some extent the ALS).
3 - Basically all airports with an IAP could have a high quality approach to each runway and as soon as EGNOS/WAAS becomes operational they could have a virtual ILS to each runway.
It obviously would be much better if the CAA allowed approaches without based ATC (as in the US and many other countries) this would really open up the utility of GA in the UK.