All joking aside, considering the British Army's current deployments and possible/probable future deployments, consider the other side of being an infantry soldier.
As boots-on-the-ground teeth arms at the FEBA(look it up), infantry soldier's will invariably be the first to be captured and become POW's.
Look at the possible/probable scenario's:
A female infantry soldier is captured by the Taliban/other radical Muslim fundamental insurgents. Given the treatment of other soldiers/prisoners in recent/current theatre's of operations, how well do you think a female combatant would be treated by such? How much of a propaganda coup would it be for her to become the subject of a video message?
Should one be captured and treated in a depraved manner and possibly beheaded by opposing forces, how would the general public of the UK react?
The extremes of circumstance, location, requirements and possible repercussions of capture will far outweigh the reasons for deploying such Servicewomen.
Furthermore, sad though it is the general public have become accustomed via media, news stories, charity events etc to seeing UK Servicemen with missing limbs and all that that entails. I'm not saying that females couldn't cope in such circumstances(doubtless they could) but again, how would it sit with the conscience of the Government, Army hierarchy and public in general if we began seeing females in such ever increasing circumstances?
A female Servicewoman was recently removed form the theatre of operations in Afghanistan after it was discovered that she was pregnant. She was in Camp Bastion and had concieved prior to deployment, unbeknownst to her.
Infantry at the FEBA may be working out of a FOB for weeks at a time. What would happen then in similar circumstances?