A lot used to depend on whether it is council owned land or private land, and previously on private land the notice could be ignored dispite threats of county court action, or you could make an offer to pay what would be deemed as reasonable i.e. £5, to prevent any further action, but unfortunately a recent court case changed the private land side of it stating that a penalty of £85 for an infringement is reasonable (maybe on a County Court judges wages - certainly not mine, but that's another story). So unfortunately, if the signs are in place then it's looking like you may have to stump up if Lidl themselves don't sort it.
Council owned land is still the same - they have you by the short and curlies and there's very little you can do. All the exemptions are on most Council parking websites.
I've been through this on three occasions in recent years - two were mine, one my wife's. I was successful on the first on private land, the second on council property I had to pay, and the wife's on private land was after this Court ruling, so again, we decided to pay as it now just can't be ignored as previously.