Cross currency invoices

[Ed W <..hidden..>]

OK, so I have only sterling bank accounts, but I have an invoice from a 
supplier in USD.  I go to the bank and buy dollars using sterling and 
then wire the money to the beneficiary

....Now how to best enter this into the accounts system

I had previously been taking the rate that I got on my USD transaction 
and converting the invoice into stering at this rate, but it's awkward 
and error prone.  I now want to use the accrual type system and an FX 
account.

So I enter in the invoices in USD.  I then use the "payment" function to 
pay the invoice in USD, which I believe will leave me with a calculated 
GBP amount against my cash account.  Now the remaining bit is how to 
post the balancing item into an FX reserve account so that the correct 
amount of GBP is shown...?

Can anyone talk me through the best way to do this last step please?

Cheers

Ed W