The general advice would be to get your valuations after you get your professional advice. Your advisor should be able to specify what they need to have included in the valuations. If you get valuations beforehand there is a high chance that you will need to have them re-done later on.
By the way, if you don't mind me saying so, the "advice" you received from this "tax specialist" seems to be an absolute joke. If the "tax specialist" is a practising, accredited accountant or tax consultant, you should consider reporting them to their Institute. If not, then you should only accept advice from a practising & accredited advisor. The scale of potential CGT liability in this scenario is much too large to warrant amateur "advice".