My screen came quite quickly, I would certainly recommend the source as there communication was good and delivery quite fast.
I didn't get time to perform the neccesary surgery staright away as I am snowed under at work.
In the meantime I bought another faulty 505 off ebay that should have come "in the original box with all the acessories" but instead came in a PRS-600 box with no case, which is waht I was really after.
When I finally got round to it and connected the screen to the original reader it emitted smoke from the motherboard and a rather bright orange glow as one of the IC's self-destructed.

I had a PSP charger plugged in so I suspect that the full 2A went through it for whatever reason!
It was a couple more days until I got round to trying it in the second reader and it worked fine

thank goodness! I have just finished chipping the old screen off the frame (it is so thin that it breaks up then removing as it is stuck over the whole back of the screen) and cleaning off the glue with nail varnish remover.
I now need to find out/decide what to use to stick it to the frame as I suspect that too rigid a glue won't allow any stress relief as the frame expands/conttracts over temperature. If the adhesive is too thick then it will mean that the assembly may overstress the screen when fitting it back into it's case.