I wish to offer a different perspective - first your wife will be treated as having owned the property from the purchase date - as this was both your main residence when you made the transfer.
Second - the additional private residence relief of 36 months (if the property is sold before 05/04/2014) or 18 months (if sold after 05/04/2014) only gets awarded when you sell a property that is NO LONGER your main residence, and you indicate that this is your current home, so unless you move out and then sell, will you even need to worry about the additional relief being 36 months or 18 months in additional to the actual time you lived there.
Thirdly - the Private lettings relief element due, is awarded to you both - but just for the period when the property was let (so is time apportioned to reflect the catual time you had tenants and of course is on the expectation that all rents were declared to HMRC)
Then we have the period of time when you could not occupy the property due to you moving for work in London - this period MAY qualify for private residence relief too. Plus when all reliefs and other deductions are made (so costs to buy and sell such as legal and estate agent fees and stamp duty and the costs of any major improvements ( for example such as new kitchen, conservatory, new roof etc) then you STILL have the first £10,900 EACH exempt (this increases to £11,100 after 05/04/2014 and is your annual exemption allowance awarded in the year of sale)
So you may have very little capital gains at all.
I hope you do not mind me offering these additional savings and information, but at least you are then clear on the full position. And if you wish an estimated calculation to be made then do feel free to ask another question on Just Answer, and you can always ask for me Sam Tax in your opening post if you would prefer, and the other experts will leave it for me to answer. (I'm online every day)