My thanks to all who have contributed to this thread. It's been most helpful.
I thought I'd update you on my progress to date.
While working up the new .308 loads and shooting in the new rifle I've gone back to using Sako 100gr Gameheads (lead core) in my .243 for actual stalking and been much reassured by the improved "knock-over" power of that round (against my Barnes TSX at 3300fps MV).
I'd been reading all over the place about what gives bullets that sort of clout and am persuaded by the argument that some degree of disintegration "dumps" more energy in the animal which gives the punch effect. So became interested in non-lead bullets that to some degree disintegrate as opposed straight expansion. Earlier in this thread Yorric drew my attention to Neilsen Sonic Hunts bullets - a brass bullet with a hollow nose, a brass plunger (to initiate disintegration and improve ballistics and feed) and pre-cut fracture lines.
I also came across the Lehigh Defense Controlled Chaos copper bullets - also designed for the front part to disintegrate leaving a solid base to pass through.
The TTSX 130grain .308's I had on order from Brownells UK (no-one in UK had any) have got stuck in transit from USA (apologies sent by Brownells who are working on it).
A mate of mine found 3/4 of a 1 Kg tub of VV N135 in his gun cupboard and gave it to me!
I was able to obtain some Neilsen Sonic Hunt in 110gr .308 (
Projectiles Practice — Store 1 — Deer Gear )
and some of their (cheaper, but ballistically identical) non-expanding target rounds (
Nielsen Sonic Lead Free Target — Deer Gear )
and
some of the Controlled Chaos copper in 115gr .308
So to stop myself going stir crazy decided to start with what I have.
I loaded up some full length resized & trimmed used Federal .308 cases my mate produced.
I decided to try the Scott Satterlee "10 round" approach - first time for me!
VV give loads for Barnes TSX 110gr .308 using N135 as 43.2 min to 46.3 max.
So I loaded 14 cases from 43.1 gr increasing at 0.3 gr intervals up to 45gr and then at 0.2gr intervals to 46.4gr
I proceeded in a leisurely fashion (during that warm still spell we had) with Magnetospeed in situ and target at 100 metres to work my way through noting the MV's. I'd never tried this before and the emphasis was on recording MV rather accuracy (though to be fair the Magnetospeed doesn't seem to adversely affect POI at that range). I had my Swaro' 8x65 on it as I want to keep the X6 2.5-15x56 on my .243 for hunting. I was amazed to watch the group shrink as the loads increased to less an inch between 44.7gr (3041fps) and 45.2gr (3045fps) before opening up again and then tightening up a little bit at a second flat spot between 45.8gr (3108fps) and 46.4gr. (3107fps)
BUT from about 45.8gr I was getting more recoil and a slightly stiff bolt lift - not really stiff but noticeably more than the lower node (no other pressure signs AFAICS). I just felt more comfortable shooting at the 3041+fps node than the 3107fps node. I dare say for longer distance and target shooting the faster node might be better but this is for short range hunting so I've settled for the 3041+fps node. It's also a "wider node" (the faster node might be just as wide but I'd have to exceed max load recommended to find out).
I've previously used Lapua cases and have more confidence in them although I believe Federal (used) cases have a good name. I couldn't help notice that there felt some variation in resistance when re-sizing the used Federal cases - I don't know if this was my imagination - you can get to thinking too much about these things! I've ordered some Lapua cases to put my mind at rest.
So I'll load a couple of dozen Nielsen's at 45.4gr and take it from there. All have been loaded such that the first driving band is just inside the neck (makers recommendation) I'm hoping that will give me sub inch groups for hunting without messing about with differing jumps.
I'm also wondering, since my barrel is noticeably more sooty than my .243/N550/BarnesTSX rounds used to be, whether I'm getting incomplete powder burn and whether a marginally faster, double base (N530) would perform better (& in the Lapua case!).
I have a supply of the Controlled Chaos copper in 115gr which I'll experiment with later - they are very clean looking rounds, almost sculptural, with really quite dramatically narrow driving bands and according to Lehigh published data are very slippery in the barrel and go fast for weight and load. They are also surprisingly cheap compared to most non-lead. I've also got some Barnes TTSX in 110gr promised any day now from a reliable source in Tain

.
Once I have the Neilson Sonic Hunt shooting to my satisfaction I'll start trying them on deer (Roe).
I'm loving shooting with the Sako 85 Finnlight 2 immensely. The light weight and balance and that adjustable cheek piece really do make it so much easier to hold steady. I have high hopes that it will give me the "knock-over clout" of the Sako 100gr Gamehead .243 (lead core) but using non-lead in a rifle that is lighter than my Sako 75 .243 and more comfortable to shoot and carry.
I'll keep you posted as to further progress and hope others will give further feed-back on their non-lead experience.
Incidentally there is an excellent paper by Andrew Yool : "Rifles for Roe" in the Spring 2021 edition of "Deer" (the BDS Journal) which would be of interest to those following this thread.
Thanks, Alasdair.