uPVC door handle problem!

My patio door handle has suddenly stopped closing properly. When I looked more closely, I found that the latch has gone all soft - you can push it in with a finger and there's no resistance. When I lift the handle to lock the door, the latch is pushed back out, but it can be pushed back in again just as easily, even whilst the locks are engaged.

I was going to take the handle apart and have a look, but I thought I'd ask on here first in the hope this is a common problem and get some advice

Thanks!

OK, I have now sourced a new latch mechanism, but am going to have to alter the frame as the locking parts will be in slightly different places. I'm just wondering what's the best tool to use to cut into the UPVC frame? The holes that are there look like they've been hacked into the frame - they're not exactly neat. I can't see that a chisel would work very well... or would it?!

A sharp padsaw blade is probably your best bet.