For occasional usage (i.e. the c. 4months/year that I actually need one) the inreach works out cheaper and has vastly greater functionality - email, text, weather reports etc. The spot feels like obsolete technology with its absence of 2-way comms.
I found a UK supplier for ev50 in low volume - pentonville rubber in London (not as dodgy as it sounds, but not an ideal name on your credit card statement!).
unfortunately, I and they thought it was ev30 I was buying, but the density I've measured means it must be ev50 so it's 150g/Sqm vs the 100g ev30. Not the end of the world, but there's quite a few ev50 suppliers and I'd really prefer the lighter stuff.