The Capital Gains tax relief you refer to is Principle Private Residence (PPR) relief. This is only available to the owner of a house if he occupied it as his only or main residence. Unfortunately, an intention to occupy it is not sufficient to qualify for this relief.
It is not necessary to have lived in it as the only or main residence for all the period of ownership, but it must have been occupied for at least part of the period of ownership as your only or main residence.
HM Revenue and Customs state that to qualify, “residence is one of quality rather than the length of occupation which determines whether a dwelling-house is its owner's residence”. A dwelling house must have become its owners home at some point during ownership even though no minimum qualifying period of occupation is required to qualify for the relief.
There is an exception to this rule if you live in job related accommodation and own an interest in a dwelling house which you intend to occupy in due course as your only or main residence. Provided it was always your intention during to live in the property, PPR relief will be available for the period concerned, even if it is being let out whilst you are living in another property for the purposes of your job.
You will therefore need to provide more information on whether you have actually lived in the property at any point during ownership, and if you have not lived in the property due to your work requirements, before we can establish whether you will infact qualify for PPR relief.