Consideration covers anything which is received in return for the supply of goods or services.
The value of non-monetary consideration in a barter transaction is the figure agreed by the parties. If it is not agreed, see the last paragraph of Business Brief 8/1995 (5 May 1995), which is reproduced below.
‘BARTERS OF SERVICES
There is an increasing number of transactions which involve barters of services. In principle, all barter transactions are subject to VAT.