Ask supporters to give £2 randomly by donating it to you EVERY time they get a £2 coin in their change.
This is the perfect container too - an Erustcan Money Amphora. It orginates from Italy and has been used for 2000 years. The tradition is that after the first coin is put in the pot, it must be fed until it is full. You put a wish in at the start. What a great way to make a pledge to raise money for your cause. What could £600 do?
Try it yourself. You will find it is addictive and your eyes will light up when you get a £2 coin.