Michael "DSM" Smith of the Times reports some detail on the recent action in Afghanistan in which two UKSF members were killed. Worth reading. How would your answer change, though, if you knew that the two companies of 3 Para involved equal roughly 50% of the total infantry force available to the British Army in southern Afghanistan? (Smith has engaged with the point on his blog. I did too, back in December.
It also seems there is a degree of concern about the air support, specifically in support helicopters. It may be remembered that the Government actually wanted to send back RAF Harriers from Afghanistan to the UK until a few weeks before the deployment began, on the bizarre principle that the whole one battalion of infantry would adequately substitute for them and would need no support. Fortunately this was eventually reversed, and the current Harrier squadron is to be relieved later this year by the Navy's 800 Naval Air Squadron.
There does seem to be a piecemeal reinforcement in progress. Last week, 3 Para and a company of Gurkhas (the only other British infantry there) were joined by a field squadron (like a reinforced infantry company) of the RAF Regiment, who are to take over security for the Kandahar air base so as to relieve the infantry for their own role. The Harrier raid, by the way, appears to have been very vital indeed. AAC Apaches are expensive, RAF Harriers are noisy, but not having to rely on the USAF for your air cover is priceless.