Your liability (or lack of it) to pay for damage to someone else's property is based upon the concept of 'negligence'.
If a court was asked to rule on who should pay for the repairs, it would have to assess whether it occurred solely because of your negligence. If it was satisfied that this was so, you would be held liable for the full costs of repairs.
However, if the court decided that the damage occurred partially because of the negligence of the other driver (through parking badly) it could decide that he was responsible for paying a certain percentage of the total repair costs (including any repairs to your own vehicle).
I disagree with Grunty. The minimum insurance required by law is 'third party' which includes all claims for loss or damage suffered by a third party. Therefore, any claim against you can be referred to your insurers. It will be up to them to decide whether it's worth their while contest the degree of liability.
Chris