if your mum is wanting to save the £2,000 for you then you would be better to put this into an ISA in your name, the money from the trust fund is yours, any money which was invested into this by your parents, grandparents etc was a gift to you, they should not be asking for this back.
Most Child trust funds are able to be turned into an ISA on maturity, I would look into this then you know the money is being invested for you and no one but you can access this