Ugh, this is horrible. Why do people think they own the road, he is equally horrible to everyone and not just the OP by the sound of it.
I would check your local Council's website for their policy on parking over drop downs - I know from checking ours that they don't automatically take action but this isn't the case for all by any means. And there is the fact that he is blocking you in. I would speak to the Police about it and ask them what you can do in the future.
The other possibility - which I would use as a last resort - is some kind of letter from a lawyer, as you have to declare neighbourhood problems when you sell a house so it would cause problems for the prat (but also your landlord). Have you spoken to your Landlord about this as well? They may not want to get involved but it might be worth a try.
Frustrating though it is, by your current numbers it is only happening once or twice a month (still too many) so although any counter-parking by you may cause it to happen more frequently, it may ease off again. Speak to the Council and the Police, think about speaking to your landlord and/or letting agent, formulate your plan of action for when it happens again and carry it out.