Bricked up Doorway

Possibly the best known disused doorway in Penwith

Rail station, Cyandour Cliff wall against platform 1?

Afraid not Penwithian.

would this be in causewayhead the walkway through to the car park and the other side of this wall would be the weigh Inn?

Obviously not as well known as I thought ... pictured on site, any number of times ...

Oi! Not the time for clues yet!
Sorry Sparky. Right town, wrong location...

Humphry Davy Grammar School.

Afraid Not.

Just found it at last after much searching today , it's at the bottom of jennings street on the back wall of the old lifeboat house

Certainly is, well done. Here is some recycled information:
The Lifeboat House, sitting at the base of Abbey Slip, was opened in Feb 1885. The first boat to be housed here was a 8 oared 'Dora'. Due to problems launching the lifeboat house was moved to Mousehole and onto Newlyn.
In 1803, Penzance was given the first lifeboat in Cornwall, however it was sold 9 years later to pay off its debts.