Hi gigglybug, The police wont want to know as its on private property and therefore a civil dispute. Try putting up a sign which says 'parking £20 a night'. If you look at public car parks you can get the wording right - something to the effect that if you park here you accept these terms and conditions. You can then sue him for the dosh afterwards. But you'd have to prove it and even if you won you've then got to get the money out of him.
You could ask him to move it and if, after a reasonable time he hasnt done so, after giving him notice, you are legally entitled to remove his car but if you do any damage to it you may have to pay if a judge decided you were not careful enough and you would have to leave it somewhere reasonable too. No you cannot tow it to the nearest scrap yard.

You could try to sue for trespass but only for the cost of any damages you've suffered and I can't see that you've suffered any from your post. However I would try absolutely everything I could before going down that (VERY expensive and RISKY route).
Then, even if all that succeeds, you've got to live next to the awkward B*gg*r afterwards.
Have you tried appealing to his better nature by asking him not to park there as you need it for your in-laws who cant walk far. If you haven't said anything to him, he may think you dont mind?
It also looks from your post as if the situation might be only temporary. I know how irritating it is but could you bear it for the duration of his building works?
We have a similar situation where a neighbour parks across our access and we really do bite our tongues because I know that it would escalate and he can be nastier than we are prepared to be. I like the blocking in idea, might try that here.

ww
Money talks - but it dont sing and dance and it cant walk.