If there is a gap in the lines big enough to park your car then you are free to do so, but don't think for a moment that it is worth carrying an aerosol can of black paint in your car! That said you could end up in a legal battle that really wouldn't be worth saving the parking fee.
The majority of parking administration is now 'decriminalised', so it would not be a 'legal' battle as it would not be a 'crime'. Final appeals against a Fixed Penalty Notice are heard by an adjudicator, who usually finds that 'small' gaps in DYL are 'de minimis' and the appeal will not be allowed.
Agree, a large gap, big enough for the whole vehicle, (not just the wheels) would be ok.