Unfortunately the complaints prcedure outlines on the link given above doesn't apply to property rentals. However, I would suggest mentioning to them that, if they do take you to court, you will state that you were in an IVA at the time, didn't realise that you could not actually be a guarantor and...

Did you have your IVA before your became a guarantor? If it was afterwards I'm surprised you were accepted as a guarantor. If it was the former, was it disclosed to your IP? If your son owes money I'm afraid the creditor can, and most probably will, come after you for the money. it was a guarantor ...

i had an iva and at the time i signed as a guarantor for my son they are now saying he owes them money was i aloud to be a guarantor and where do i stand legally