My understanding is that such transactions are outside the scope of VAT. Schedule 10B, paragraph 7(2) of the VAT Act reads:
"The paragraph 3 supply made on the issue or subsequent transfer of a multi-purpose voucher is to be treated as not being a supply within section 26(2)."
The following guidance may also be useful:
In particular it points out that intermediaries will be unable to reclaim VAT incurred in the course of this activity, as they are not making a taxable supply.