You can log anything you want. The only issue is wether the time counts towards the award of a higher rating or license. I do not know the rules for the UK but in Canada the time would not count.
However if you are a low time pilot you will learn a lot riding up front. As long as you are honest about the circumstances under which you are logging time why not put it down , if only as something to be able to look back fondly on in future years.