Owning your own home

Ask the sellers for a Statutory Declaration that they have parked there unhindered for 15 years and get them to pay for an insurance policy that indemnifies against your/the mortgage company's loss if the council take the parking away. Such a policy will probably be a few hundred sovs.

Bear in mind that generally the insurers won't provide cover if there's been contact with the person entitled to the benefit of the covenant, so either try to get consent or get the indemnity cover - it's either/or.