So... Enough thinking. Lets build.
I did as much pre-planning as I could, I thought about it some more and then eventually broke. Time to build:
Having received the last components from Tube-town - check component sizes on turret layout.
Cutting turret board down to size. Barry at AMPMAKER sells these easy-drill & easy-cut boards. DEFO recommended!
Pre-punch holes to stop the drill slipping.
Barry also sells these screw-in/nut-tighten turrets... Kinda cool idea so I thought I'd give it a go.
He also sells a specific sized drill bit to allow the turret to fix into the board. As I was stupid and used a dremel to drill the holes this precision was lost on me and the holes over-sized. I then resorted to plan-b where the turrets are fixed with a nut. BTW when drilling these boards the plastic tends to gets stuck on the drill bit. Hurts like hell with those things whipping around at 10,000 rpm!
Parts organised and ready to populate the chassis - which BTW used to be a broken MOSFET amp...
Once again - I cannot recommend using INKSCAPE enough. It is SO useful being able to mock-up things to scale... The turret board for example, and the chassis... well.
Once the metalwork was done - which goes quickly if you don't ever have to actually do it! - and the dust settled, time to stuff.
Early days turret population. I think I will re-work the dropping resistor to the ECL82. I had to piggy-back two 8K2/5w to get the 4K1/10w I was aiming for. I think I may drop this down to 3K9 to bump up the B+ a little and use one of those fancy chassis-mount aluminium 25w jobbies.
Finished populating the board and adding flying leads prior to installation.
Did a few necessary safety checks first - grounding, continuity etc... Then fire it up WITHOUT the valves. Check the filament voltage and the rectified B+... All good. Add the preamp valve only... All good... Add a dummy load and then the ECL82... Power up and... and... ANNNNDD.
HURRAY! No fire, no smoke, no burning smell. No electrocution.
Only one thing left to do. Plug it in..
Works a TREAT! Sounds great already. There is a little bit of hum but I think that is down to the 6sl7 (the little pre-preamp had the same noise when fully cranked). It is a great volume for recording. NOT GIGGING! but I do feel it breaks up pretty quickly, as such I'm investigating/asking questions about the negative-feedback suggestion...
Hopefully at lunchtime I'll get chance to record a quick sound-bite... so far I am VERY HAPPY.
Once more, a quick thanks to all the kind and knowledgeable gentlemen at GroupDIY that have helped get this idea together.