Thank you schoolmarm for responding to my post. The deeds say that the owners of the adjoining property have a right of way at all times and for all purposes. It says nothing about visitors.
Well that is a difficult one! The deeds are not very specific are they? Sadly! When they were written I have no doubt it was not considered they'd ever be really able to cause these difficulties many years later. Many, many homeowners are finding otherwise.
I would suggest that 'all purposes' may include vehicles passing and re-passing (unless stated otherwise and it's obviously a path not a road). Parking, however, is very different as it would prevent the freedom of access for others, and I'd suggest that it isn't part of what was intended in the deeds. An easement (a right to pass and repass for access) is simply that, and unless there is a specific easement for parking also (or one is claimed now by long usage) I'd be inclined to say no.
Possibly you may need to discuss this more fully with a solicitor specialising in land law. If you have it, check first that you have legal cover in your house insurance, these things can get very complex if the neighbours won't agree!
I agree - it's just if parking has gone on there with the land owner not objecting for a number of years, a claim could be made that a parking right has arisen through prescription of one form or another. This is why some advice about how to proceed may be needed. I think that would only apply to the neighbours not casual visitors however.
Certainly, a letter to the neighbours (keep a copy!) or a notice placed on the land is possibly required, if a friendly chat isn't possible.