Thats absolutely fantastic!
Thanks so much.
I have made the adjustments you suggested above and the PayPal button now works and a receipt comes through in GBP.
I have removed the form from below the button as that was not working, and if this PayPal button is working I see no need. Every thing writes back into the database correctly.
One last issue, for some reason it is now not displaying or showing the UK VAT Tax rate (15%). It did before when it was USD.
The tax rate is still in the eCart definition, and active, but not showing in pp_confirm.php or on orders.
Same with a charge of £2.99 for postage, it's in the eCart but not showing on invoice and pp_confirm.php page or on orders.
Many thanks for you help, nearly there.