This probably doesn't help, but:
I funded my broker account (Ffasttrade, part of MAN group) by using my NatWest online to send them GBP to their bank account at Bank of America in London. Usual sort code etc.
I only trade FTSE etc, so my core balance remains in GBP but I rack up commission in USD. That then accumulates over a period of time into a fairly large negative figure, in a column in my statement.
The other day I cleared that, by emailing them. They "bought" USD at 11.00 EST the next day (which is their set time for that procedure), and cleared my USD column, with a reduction in my GBP column. I think they just used the bid price at 11.00. It was 1.9432 and no commission.
All fairly painless.
Maybe TS8 can do the same thing if they have a GBP account in Blighty.