just look up more about innocent purchaser defence.

You will probably find a template letter that contains the pertinant points. If not, the law isnt too long or complicated so you can qoute away.

Get the first blow in early Should things turn nasty, it would look bad on the finance company in court if they recieved a letter claiming the defence and seized a car or aggressively pursued a debt without investigating the defence properly.

Oh remember send it recorded and CC it to the solicitors (even put it on the letter that its cc'd to xxx solicitors). Covers your back if they try and deny it and also will show them you are serious now by having copied it to your solicitor. Doesnt really matter if you cant see them until tuesday, its unlikely the issue would have been properly looked at let alone dealt with by then.