[V40DSchariot]

What's happened since re-filling the brake fluid, has it held that level or still dropped?
Where was the new caliper purchased from?
I see your down in Brighton and ironically while I was down in Brighton a couple of years ago I had total brake failure which was caused by a replacement rear caliper that had rear seal failure, which was brought refurbished off a common auction site as recommended by some users on here, might have been in use for 10mths.
Anyway, this resulted in every press of the foot pedal a large squirt of fluid ejected from the faulty seal.
I ended up going to EBC motor factors in Brighton, where I purchased another rear brake caliper and who kindly borrowed me the necessary tools to complete the job.

So, if you can, and if your still losing fluid, get someone to push the brake pedal while you look around for leaks, and get some goggles on, you don't want to get brake fluid in your eyes.

Driving around a housing estate, down a hill with a bin lorry in front of you with nothing but a handbrake for braking is'nt as much fun as it sounds, trying to get to the nearest motor factors.