If he gets to keep the car after the claim has been settled, once you have had the work done you will need to get the car VIC checked and re-mot it and re-apply for the log book.
Absolute shit,what are you talking about,re Mot the car?how do you know it's cat c?
To the op,I'm in the trade mate,keep in touch with the company and explain the damage is very minor but you'd like to keep it as it's got sentimental value to you,usual bullshit.
You MAYBE asked to take it for a vic check but this is nothing to worry about,it's a VEHICLE IDENTITY CHECK which translates as you give the government £41 to tell you that you didn't ring your own car!!bonkers eh?although often as it's your car you may well not need too and as you'll probably retain the v5 you won't need to do this straight away.
As for re Moting it that's just utter shite,never heard of that in my life for cat c or d,it's just Internet bollox somebody heard down the pub.