I. Don't. Believe. It...

 the period feature

works at fucking last

Why? Prayers to the chopper gods?

Paul made a surprise visit just as I'm about to take the caliper apart and put together my old one and try that.

We gave it just one more try and back filled it, and bingo, a little pressure, it seems you need the master cylinder cover on. 

However it wouldn't back fill before till I'd replaced the master cylinder internals and thats why I thought it had a non return valve.

So loads of pumping later and its acceptable.

Of course the brake light don't work -Haha