Many years ago I had a go at driving someones Robin Hood, a similar size and style of car. This had the master cylinder and servo from Its donor. I found it very hard to brake, with the fronts locking up almost instantly with only a slight touch on the pedals. I suppose with more miles driven I could have adjusted to the feel, but I felt it just didn't need the servo.
You have to push a bit harder, but you have good control and feel of the braking force on my Westy with the standard master cylinder and Cortina M16 front calipers. You can take them all the way to lock up no problem. It feels different from the heavily servo'd brakes on most modern production cars, but I prefer it that way.
Do you know, or can you measure the diameter and hence surface area of the pistons in the front calipers on your car? The area ratio compared with the master cylinder pistons would be useful to compare with other Westfields. It may be that the Midilites need a different master cylinder to get a reasonable force for your leg to press when braking.
Jen