Hi,
With regard to the prices in the UK, if you import UE's, as I did, direct from the US you are liable for VAT and import duty together with a customs clearance fee since they use Fedex. So the additional £300 is not as excessive as it first seems.
I telephoned several hearing centres and found one that was used to doing custom moulds for hearing aids. Print out the instructions from UE and Sensa and take them with you. Keep your mouth reasonably open whilst the moulds are being taken, not stretched wide open. Mine cost £30 and my UE's fitted OK first time. Initialy I thought they were not tight enough, since I'd been using ER4's and there is not the same isolaton. However, when I inserted them correctly and realised this, they were fine.
I walk around , drink, drink some more and no loss of seal.
If you go for Sensas, they will ship as a gift under $60 so avoiding duties etc. The downside of this is if they are damaged or lost in transit, you can only get $60 back from the carrier since that is the declared value.
Hope this is a little informative.
Regards
John