Hi Colin, apologies for the ridiculously late response, life doesnt get much busier than mine is right now.
The answer is that it depends how handy you are. Great frames can be made by skilled people with a hammerand nails, a saw and a hand glass cutter. Even mounts can be cut with improvised equipment. I however am not that handy
If I was serious about doing my own without spending thousands on equipment I would be looking at a mounted hand mitre-saw. These seem to start at about £50.00 but £150.00 wold get you a capable bit of kit. Im not sure how these cope with heavily finished mouldings but I would imagine that with practice and a sharp blade you could do most things.
I would then be looking at a corner pinner for joining the mitres. Again I would go bench mounted, the Frameco Benchmaster is allegedly a pretty good place to start, and coupled with a strap clamp you should be able to acheive pro quality joins with relative ease. Again about £150.00 should see you right here.
I would cut my glass by hand as good gear here is pretty exensive. A good hand glass cutter can be grabbed for 25 quid and should last years.
Backboards can be cut by hand with a stanley knife so no problem there.
The last thing ofcourse is a mountcutter. I have no experience with low end mount cutters so I cant really comment, but you can pick up a hand bevel cutter fo £15.00 and ive seen people do acceptable work with them. I use a Keencut Ultimat which cost me about £700.00 and I would not cange it unless it was for a serious upgrade.
My best friend in my wokshop is my metre long steel ruler!
I hope thats helpful. If you have any more questions id be happy to answer them..... albeit slowly!