Do kids have their own allowances for taking goods or even duty free into UK? Is there any published set of rules about this I can refer to?

Thanks for your help...

Children get their own allowances except that those under 17 do not get a cigarette or alcohol allowance.

For entry from outside the EU..... https://www.gov.uk/duty-free-goods/arrivals-from-outside-the-eu

The HMRC rule is:

"You can bring some goods from abroad without having to pay UK tax or ‘duty’ (customs charges), as long as they’re for your own use".

So children will not be given an allowance for alcohol or cigarettes and you're almost certainly not going to be able to get an extra 'Rolex' through customs by strapping it to your 3 year old.

http://www.dutycalculator.com/