Hi Rob, thought you'd legged it, nice to see you back... to get more gain on the front end you could use an 81 or 83 instead of the 82 and lose that 470k grid stopper on the 2nd half of the 82. I'd have more idea if I knew the HT at the front end, which looks to be about 250/280v without doing the calcs.
Do you know how to draw a load line? See -
http://www.valvewizard.co.uk/gainstage.html on how to this, it is easy to do for a common cathode triode gain stage. This will give you expected gain, cathode R etc before experimenting or you could just breadboard it and wing it. Something like bung in a 83, reduce the first stage Rk to 1k/1k2, lose the 470k grid stopper on stage 2 and convert it to a cathode follower to "drive" the tone stack or reduce 2nd Ra to 33/47k and reduce Rk maybe.
A few thought's on the circuit - 13W is really pushing ECL86's, fine when they were 1p a dozen, not so fine now. Do you really want the tremelo? It's a bit Grandad on a tele playing twangy 50's rock n roll; lose it and the second valve and drive the LTP from a high/low gain stage. Just thought's.
Andy.