Setting aside a CCJ. All correspondence sent to wrong address. Help?!

I became aware of a CCJ on my name when I was recently applying for a mortgage (now on hold) in December 2015. After enquiries, I’ve figured out that this was pertaining to a parking ticket during a holiday to Wales with the family in August 2014, when we made a trip to the Rheidol retail park in Aberystwyth. They posted the parking ticket to the wrong address as I had recently moved and DVLA hadn’t yet updated my address. I have applied to have the CCJ set aside and I have a hearing on Monday 7th March, 2016. I have spoken to Citizens Advice Bureau and Debt Line but they are both suggesting that I seek legal advice as they feel I may not have sufficient grounds to win this case.
any ideas or help?
Added (1). Any advice on how to prepare or should I withdraw and pay the CCJ off? If so, how will that affect my mortgage application? Any ideas?
I was renting at the old address and the owner agreed to forward my mail but didn't and eventually sold his property and moved abroad.

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