Aside from the merits of the case, which you both appear to be covering, it would be useful if you could set out a time line, with exact dates, of all communication between you and VCS (or any debt collectors/solicitors acting on their behalf).
Whilst there is no time limit for set aside, courts expect them to be applied for promptly. Obviously, if you've only just found out about it now, you are acting promptly, but you'll need to be able to explain to the court why you are applying more than 5 years after the judgement.