In ball park figures, females comprise roughly 10% of the RN trained strength.
Figures aren't available with regard male/female percentages by trade, however trades such as Naval Nurse, CIS, Writer, Medical Assistant & Supply Chain Logistician generally have slightly a higher than average percentage of females at Able & Leading Rate whereas engineering trades have below ten percent females. Bear in mind that in some cases females elect to leave the service if they marry or decide to have children for practical reasons whereas statistically more males elect to remain within the service, so females generally serve for significantly shorter duration on average.
The last available figures (July 2010 Naval Service quarterly pocket brief) for trained strength by rank and gender are as follows:
Flag Officer 40 males, 0 females
Cdre 70 males, 0 females
Capt 250 males, <5 females
CDR 1 ,010 males, 30 females
LT CDR 1 ,760 males 190 females
LT 1 ,980 males, 370 females
SUB LT 40 males, 10 females
Total 5,150 male Officers 600 female Officers
WO 640 males, 30 females
WO2 570 males <5 females
CPO 3 ,280 males, 180 females
PO 3,580 males, 340 females
LH 4,200 males 700 females
AB 7,390 males 1,440 females
Total 19,660 male Ratings, 2,690 female Ratings.
http://data.gov.uk/dataset/royal_navy_pocket_brief