I have a Performance Power Tools cordless grass trimmer which has run
out of line. Its been so long since I last did it that I cant remember
how to take the old reel out. The only screw I can see is to hold the
protective shield in place. I cant see a screw on the shaft to hold the
reel in place. I've tried pushing & twisting but the bugger wont come
off. I know its got to be something simple but I'm generally a bit
clueless so...

Any suggestions please?

Have you tried turning it anti clockwise?some times you need to give them a shock to get started,as they stick on the threads,assuming it is screwed on!
hope this helps.
Grumpy.

I ment clockwise, but who knows,either way might work!
let us know how you get on.
Grumpy!