...I don't hate crabs, as a matter of fact they make me look/feel good!
On the subject of ASTOR, the capabilities of the system are highly confidential, so you won't get much more than the stuff you've read already. You can rest assured that it will be a potent piece of kit that will give Land commander in particular a God's-eye view of the battlefield in real time.
Suitably cross-cued, it could be a mainstay of Network Enabled Capability for many years to come - if we had any networks of course! No networks = no NEC, but no one seems to realise that in London yet...and that's another subject.
anyway, on the subject of UAVs, WATCHKEEPER will have a SAR as well as EO/IR etc. Saying that UAVs should be used instead of ASTOR though rather misses the point. ASTOR is to WATCHKEEPER what an artillery gun is to a sniper rifle. They're similar on paper, but designed to do different things.
On of the problems that SAR places on its bearer platform is the amount of electricity it uses in the radar; bigger aircraft not only carry more payload, but also produce more electricity. You need look no further than the USAF's efforts to produce the EB-52 for an example of this - 8 engines = a fair bit of juice = ideal Electronic Warfare platform.
A small aircraft like a UAV (even though the WATCHKEEPER UAV has approx a 35 foot wingspan) won't produce as much power as ASTOR so propbably wouldn't have the same range - but it doesn't need it. It also can't carry the same payload. The added advantage of ASTOR is that, although it has a ground element to process its information, it doesn't need it in all circumstances; UAVs do. Quite useful if you want to recce areas where a ground system cannot be deployed within range.
So Ivan, you may say that UAVs are coming along that can do the ASTOR mission such as Global Hawk, for example, and you are right, but something like GH needs serious space communications support, something that the UK is only beginning to work up to with SKYNET 5. Also, the MOD's airworthiness branch are very circumspect when it comes to UAVs (the tank will never replace the horse as far as they're concerned) and are scared to death of the Treaty of Rome, so they won't let UAVs fly without swinging restrictions - something that doesn't affect ASTOR. If you add the cost of SATCOM running at 10Mbps, the actual satellite, the risk, the UAV (GH is still officially experimental) and so on, ASTOR looks like a good bet after all.
UAVs are probably the future for ASTOR-like capability, but they are in the future. To deliver something like ASTOR today in a UAV would be much more painful, risky and expensive than doing it the way it has been done with ASTOR.
...Plus the airforce get to fly a few more executive jets than they do now, and that has to be a fringe benefit for anyone thinking of leaving the service...