Provided there is no right to park on the drive and it is either owned by you and the neighbour has access over it or it is owned by the neighbour and you have access over it, then the neighbour parking on it and denying you access, it is substantial obstruction and is enforceable through the county courts.
Clearly, the tenant is taking no notice of you and hence you might want to do is to get a solicitor to write to both the landlord and the tenant threatening court application if the occupier continues to obstruct your access. It doesn’t matter that you want access 100 times per day, they are not allowed to block it.
The letter from the solicitor would threaten an application to court for an injunction to “cease and desist” from parking and would threaten an application for the substantial court costs and solicitors costs involved in making the application for the injunction.
Provided there is no right to park and it is, as I said, either owned by you and the neighbour has access over it or it is owned by the neighbour and you have access over it, then the neighbour and the landlord would be ill-advised to go to court because they will lose and get legal costs awarded against them.
Your action being threatened would be against the tenant for doing it and the landlord for allowing it to happen. Fortunately, you have lots of photographs (hopefully with dates) which can prove that this is an ongoing substantial obstruction.
Can I clarify anything for you? Please rate the service positive so that I get paid. We can still exchange emails. Best wishes. FES.