https://www.paypal.com/uk/charity/
I have not investigated this ie read all the small print but it could offer a solution if eg TZ UK set up its own charity and was successful in having same approved and registered in accordance with UK charity regulations. To try and raise ££ without expecting 'the bank' (in the broadest sense of the definition) to take a commission would be a bit naive - no bank or Paypal or charity middleman provides a service for nothing .
If TZ UK wants to make a go of the charity idea then you should expect to incur costs - and reasonable administration time - and as long as those costs are reasonable then the proposal should be cost and donation effective.
Don't expect to do this 'for nowt' .. and make sure someone has the time and inclination to administer the scheme.
dunk