Technically I was wrong. Apparently on Who Wants to Live Forever The National Philharmonic Orchestra was used. Here is an excerpt:
The National Philharmonic Orchestra:
This was recorded separately at Abbey Road Studios. The score was arranged by Brian with the help of Michael Kamen, who famous for his scores for movies such as Highlander, Lethal Weapon-series and Die Hard as well as for his arranging-work for rock-groups. His last big deal was his collaboration with Metallica (after Queen, my second favourite group).He arranged their material for a symphony-orchestra and the result was their latest album, called S&M.
Back to Queen: Michael Kamen probably also conducted the orchestra (it isn't stated on the sleeve, but he arranged and conducted all the scores for the film where Who Wants To Live Forever was one of the main-themes, so it is quite probable that he also did the conducting-job for the album. As arranger he knows the score best!). The orchestra was recorded by Eric Tomlinson, who seems to be an expert for orchestra-recordings, cause this bloke also recorded the orchestra-parts for the Flash Gordon-soundtrack (another Queen-project). The world is small, isn't it?
The National Philharmonic Orchestra is quite a big outfit.
It consisted of a huge string-section (I'd say at least 40 people), consisting of violins, violas, cellos and double-bass (kontrabass).
Apart from that there were 3-4 french horns, about 3-4 trombones, about 2 trumpets, a harp, some flutes and a percussionist with a big bass-drum and a cymbal und such stuff (see above for details).
I've never been there when a big orchestra is recorded, but I suppose it's done with a big room (with a good acoustic) lots of microphones and a control room.
Mr. Tomlinson did a good job (obviously) and there's some nice stereo-panning, but it's far to much to go into detail. Check it out! http://queen.musichall.cz/index.php?s=ps&d=wwtlf