My mum and dad live in Bournemouth, wonder if the old lady would write a receipt?
Not such a daft idea, actually. When I was at CATC we all tried to go on OJT placements near where our folks lived so we could stay with them. Get them to write you a receipt for contribution to household expenses/rent/whatever and claim the £100 as usual. Most students had their own receipt book that you can buy from a stationers for just this purpose.