Thanks for the info Arjan and Gordon – you are correct. The bases are made by Jukova Corporation Oy Tel. +358 10 474 4241 firstname.lastname@example.org and I dealt with email@example.com who looks after these products and speaks good english. These ones were the AS097 model and they had 66 in stock. I ordered 20 (I need 18 and planning to fit two more to strengthen the push-pit where the liferaft is attached) and this cost €20 a unit plus VAT at 24% plus €60 carriage to the UK.
I will let you know how I get on with fitting them. Only two bolts into the rail – phew.