I know Kaz lol, and I think either would be a bit of a problem 'cos aren't unbaked cheesecakes usually cream cheese with cream of some sort...I presume the cream is what helps it set, as well as make it not just cheesy
Don't know if anything like creme fraiche is available either; you could make something mixing cream cheese and thick yoghurt, sweeten it a bit then layer it with the bashed biscuits and eg strawberries.
I can get creme fraiche at Intermarche, that's the only supermarket that stocks it on a regular basis.
Other than that, I'll just have to google and see what I can find.
Our cream cheese is vile and although we can get a version of cream, it's nothing like the "proper" cream I'd ask Jenny, but her mum is really ill in hospital and I don't want to bother her.