Whew, what a relief! I managed to pull apart the bow, mind it was a hell of a job and I ended up falling backwards at one point as the bow pulled out of the vice.
The pics pretty much tell the story. But here are some details.
I bought Epoxy resin and hardener, a reel of 1" glass tape and some spray mold release wax which cost about £35.
The resin should be mixed in a 30:100 ratio, but I checked the data sheets and went for 25:100 (or 1/4 as we sometimes call it!) This was to give me a longer pot life, but as it happens it would have been fine as it was cold in the garage. In fact I ended up with the old "will it cure?" anxiety!
Wrapping it up was very straight forward, and I'd have got away with mixing less resin, but I didn't want to run out. I mixed 400grains of resin with 100 of hardener. I reckon 300 would have been ok, certainly for a longbow. The finished wrapping was covered with clingfilm to stop any loose ends of glass popping up, it also allowed me to squeeze it and shape it slightly.
The two halves of the bow had been pegged together with a 3mm bamboo skewer to hold it alignment while wrapping and that's what was worrying me ... would the bamboo peg shear when it came to taking it apart? Should I have used a scrap of softer wood or a toothpick?
Early this morning I strung the bow to help crack some of the excess resin around the ends of the wrapping. and to flex it a bit. I the clamped the lower half of the grip in the vice and heaved and waggled for dear life, at one point flying backwards into my shelving, fortunately I smacked into the vertical support pretty much square on, with the impact nicely spread up my whole back, rather lucky as I could have easily hurt myself on the assorted clutter. (I really must move that pile of Zulu spears which are standing point upwards in an old dustbin.... [joke] )
A bit of a gap soon opened up and I knew I was on a winner. Banging the lower nock on the floor (with a bit of carpet there) shut the joint again so that I could give it another good pull an open it further. The open/close/open was an attempt to break off the bamboo peg.
Once it was about half way out I used chunk of soft pine as a drift to tap against the the shoulder of the right (upper) limb, the impact help finally pop it free.
Once apart, it was V tight to reassemble so I rubbed it with chalk to find the tight spots and very gently relieved them with some 120 grit paper wrapped round a flat file. I didn't take any off on the fore/aft direction, as that had some built in taper to help it out. It's still tight, but will probably ease of, I didn't want to over do it and make it sloppy.
I'll clean up/reshape the glass using metal working files (no power tools as glass dust is nasty). A wipe of rapid epoxy will seal any exposed glass and then re fit the leather grip.