10 heaters, 3 x 3.4Kw + 7 x 1.7Kw spread across 4, possibly 5 - need to
double check, separate rings. No more than 2 x 1.7 and 2 x 3.4s on any one
ring.

When you say ring, you mean general purpose socket circuit? When you say
2x1.7kW and 2x3.4kW on one ring, you mean 10.2kW, or over 42A on a 32A
circuit shared with other things? You've got a lot of diversity to find to
get that lot working!

Christian.