I fianally got around to removing my rusty old cooler pipe and taking it in to the local stainless fabricator (Acumen in Hereford) and they knocked me up a stainless copy, including welded fixing brackets, for 90 quid. They couldn't flare the pipe ends to match the original however, due to the hardness of the stainless. Whilst Jubilee clips would probably do the job unaided, I didn't want to risk having the pipes blow off under pressure, so I got a couple of 10mm brass olives from the local plumbers' merchants and had them crimped onto the pipe ends for a further 20 quid. I'm told that given the right flux and silver solder it should have been possible to solder them on, but no-one around here had the right stuff and I don't have a torch capable of getting it hot enough. Having said that, the crimping has been professionally done by an engineering company and I'm assured it will be secure and oil tight. It looks solid enough and was considerably cheaper than buying all the gear to do the soldering. Hopefully differential expansion of the two metals at the temperature of the steering oil will be within the limits of the crimping!
If all goes to plan, I now have a cooling pipe that will last longer than me, for little or no more than the cost of a replacment mild steel version. Assuming it fits OK (unable to check until the new rubber mountings arrive), all that remains is to bolt it on and bleed the steering. Is this just a matter of filling the system with the front wheels raised and moving from lock to lock a few times, or is their some other satanic ritual involved in bleeding the steering on a '97 2.8?