brains,
When you sign a contract and/or nominee, that means that you can 'nominate' someone else to take over the contract prior to settlement.
So, if you go in and sign, Brains and/or nominee, and then decide that you want to settle the contract in Mrs Brains' name, you can do that, whereas if you just signed the contract in 'Brains' then YOU would have to settle the contract and become the registered owner.
(Yes, I know you can ask the vendor to re-sign a new contract under the same conditions, with the new name, and no penalties, but the question was re the nominee clause!)
The other thing that this clause is used for is assigning the contract in the case of you onselling it to someone else. This has Stamp duty implications which you may have to discuss with your solicitor to see whether they apply...
The only thing you need to be aware of in this case is that if you sign for the property with the intention of onselling it to someone else, you must be prepared to settle the property in the event you don't find someone to take the contract over.
hope this helps
asy