Well things are moving ahead.
I've exchanged a few emails with Peter from SDM & a "ball park" price has been discussed for a 20" f5.
At f5 I'll still need a ladder, but only a short / small one (I'm 6'4"). I can handle that.
Peter believes he can have one ready to my spec by the end of the year, which would suit me just fine.
All I need to do now is find the money.....