[Warning Light] anti theft fault message 2009 Berlingo Multispace

[Jelevents]

Hi still having problems with anti theft message coming up on dash, however I've found if I turn on ignition on then very slightly turn the key but not quite enough to engage the starter the triangle with ! light goes out and car starts fine.
So far I've replaced the transponder ring and ignition switch and tried the BSI reset, neither made any difference, this morning would not start at all with either key so I disconnected battery left it all day reconnected still get the message but now starts again with both keys??????
So I'm thinking perhaps a new key would be the answer, but I don't have the pin code and main dealer or local specialist are booked up till mid October.
Is anyone on here able to plug in to diagnose fault codes I'm based in Bedfordshire but happy to travel a reasonable distance to find the answer?

Update.......I've now changed the com2000 unit on the steering column, made no difference I obtained the pin code took to a citroen specialist he found fault code F4BA but could not clear it, tried recoding the keys no luck then wouldn't start so disconnected battery started ok, but he had no idea what the fault is.
Currently not starting unless battery disconnected and left for while, anybody got any idea/ advise?
Car has done 177,000 miles and has noisy camshaft chain, egr n/w and front suspension lower arm bushes will need doing b4 next mot so I'm thinking it's time to sell it for spares or repair and try to source a replacement?????