Ok, so i updated psp to 5.00m33 and noticed the psn on the xmb but it wanted another update to access. There is no official 5.01m33 but there is a trick round it.
I found a guide on a few sites that didnt work but i corrected it a little and got it to work fine.
Download the 5.00m33 update from your preferred source (i used pspiso)
Start the updater and allow it to download the official 5.00 firmware.
When it has downloaded, allow it to verify the files.
It will now prompt you to press x to update but DONT.
leave it as is and remove the memory card.
Download on your pc the official 5.01 update, it will be named EBOOT.PBP
Rename the file 500.pbp and put it into the update folder on the memory card and overwrite the one already there.
put memory card back into the psp (still on black screen prompting x to udate)
press x to update.
Thats it. Custom firmware and access to the Playstation network.