Parking blocking the pavement is an offense as it is causing an unnecessary obstruction to the public highway. Your local council if correct and they are not able to issue a pcn for blocking the pavement, but the police can.
I am quite certain that if you made an annonomous complaint to the police that they would have to take action, as not doing so could leave them open to law suits. If you mention that it is affecting a disabled person, they are even more likely to do something.
What if someone walks in the road because they can't get past on the pavement and gets hit by a car (I appreciate that this is quite unlikely in a cul-de-sac)? If the police were aware of the problem, but took no action, they are responsible.
Tapatalking. Sorry for any typos and other randomness.