Extended skills posts to meet your clinical interests are negotiated between you and your GP specialty training college. Each college offers different options.
Once you have been accepted into GP training, talk to them about your interests in advance. This will help your college plan out your GP training.
For both colleges, these skills can be undertaken any time after completing core clinical or hospital training. The needs of the community in which a GP registrar intend to practise should be taken into consideration when making the choice.