Wetsuit vs Thin suit

Anyone know of any open water swim centers that have speedo Thin suits or similar for trial. I have a 2XU c:2 and although doing the job I wanted to have a look at going a bit more flexible but keeping some neoprene.

Speedo Thin suit has 1mm coverage on the torso, instead of 5mm and 1.5 around the shoulders for the C:2, however much the marketing guru's try and convince me, I am slight and don't have gorilla shoulders so my recovery stroke and fore stretch are the week points and noticeably tire approaching 1500, or later in 3.6k swim. I am average 1hr for 3.6, 22min for 1500 and sub 6 for 400. So I wanted to know if the reduced restriction from the Thin suit would allow my recovery stroke and stretch to out way the loss of boyancy.

I figured the only way to tell is to try, hence question as to whether anyone knows any open water swim centers west of London that have these for trial.

Cheers muchly