Ok, I've had a good look around the internet and have found many people have had experiences similar to mine when using PIC16F628A, some people have found a cure that works for them but nothing at this stage seems to work for me. Neither my PICkit 3 nor ETT programmer will recognize the PICs after they've been programmed, neither will they do anything to them - ie erase. I've tested the VPP while erasing and it runs up to 13.4 volts four times for a period of about 20ms.

I've turned code protect off, i've turned MCLR on, have tried different programming voltages but now I just have 15 PIC16F628 chips that I cannot write to.

It's getting so frustrating, if not for the cost of the components, but I've spent four whole days on it so far and gotten no where. I think it's likely to all go in the bin soon.