How to Process Payment after import of bank transactions

[John]

I import bank transactions using the standard QIF file and under the Transfer column the entries require to be allocated to accounts. 
For a lot of entries I then want to allocate various payments and receipts to Vendors and Customers (matching to invoices so the Ageing reports work), 
but the only way I can see how to do this is manually enter the bank transaction again via Business> Customer / Vendor>Process Payment and delete the imported entry!
There must be an easier way!
Nb. allocating just to Accounts Receivable or Payable is insufficient as no matching to a specific customer / vendor invoice takes place.
Can you please help.