Hi ShaunD.
Immobilizer, may not be a good idea. There were problems with the early ones. My dealer is installing an under dash cut out switch. Probable a better and cheaper option.
Waterproof leather, £1000 extra. An after run clean with Glip tone may be better.
Heated seats tend to run on the hot side.
Use standard tyres for running in. And then source them yourself.
Saves more cash. Morgan recommend 22 psi for the fronts. 25-29 is a better bet.

BRG will look good with the Tan leather. Cream or Burgundy is a classic combo as well
BRG html colour code is #014225.
You might like to try Brunswick green as well #1b4d3e.