Just to satisfy your curiosity..
On the contrary, TA SAS are usually very effective. There are two units, 21 and 23, 21 used to be in the Duke of Yorks Barracks on the King's Road in Chelsea with 10 Para, but the base was sold off by Mogadon Broon and their old head shed is now a fuggin antiques dealership. The lugbrious locale thus attracted a lot of City folk and public school chaps. 23 used to be in Leeds (!) it's Newcastle or Brum now. All the candidates go through selection like 22 and have to be similarly proficient in skills, but the TA selection has a couple of the final regular selection elements cut off (a month in the jungle being one). Quite a lot of ex-22 as well as ex-Army join the units.
The TA guys are usually individual combat replacements or get tacked onto 22 for specific missions. They often have specialist skills, for example some of them are professional medics/surgeons in civilian life. Sometimes the regiments even get deployed as an entire sabre squadron: in Gulf War 1, 21 infiltrated Kuwait and nicked a load of new SAMs the Iraqis had deployed and the Allies wanted intel on... before the war started! During Bosnia loads got deployed on recce missions, then went in during Op Deliberate Force in 1995. Also loads were on mission for the somewhat feverish Kosovo-Sierra Leone-East Timor actions from 99 to 2000 which came in rapid succession. Many now get rotated through Iraq, Afghanistan is left to the regulars though (also as use of SF via the NATO command is totally ineffective at the moment, the war is being fought in a very conventional and counter-productive way).
The full time officers in the units are from 22 so gives you an idea of how the professionals value the TA sister units.
As for Chris Ryan, his account of B20 "The One That Got Away" is a bit controversial as some of the stuff he mentioned in the book wasn't mentioned in his debrief. Since then he's worked on fiction, squirrelled away in the North as he doesn't seem too popular in 22's home town, but he is a good guy so dunno what all the fuss is about. Years ago a rather good TV movie was done with Marwood himself Mr. Paul McGann as Ryan, methinks the director was Greengrass who's now done the Bourne Ultimatum. Some of it is quite realistic.
To round all this off nicely, Ryan got into 22 from 23 in Newcastle. Michael Asher, author of "The Real B20", explorer, and biographer of T.E. Lawrence, was another guy who completed selection with 23 in Leeds.
And, just in case you're wondering, the TA units don't do the Counter-Terrorist role. With the bureaucratisation of UK SF into US style "SF division" muppetry it's not clear if the TA units will survive long term. Skillsets being duplicated in two other p%sspot "reconnaisance" regiments.
Anyway, all this reminds me that a return to full time AF muppetry is long overdue.
