Welcome to Metro! Once you are logged into the website, click on 'Contact' in the top right hand corner of any page. Under 'Subject', select 'Transfer of Hours' and just explain the situation and they'll be happy to help you.
Keep in mind, only 40% of your FlyUK hours will be accepted so as of now, according to your FlyUK forum badge you would be able to transfer a total of 49.2 hours (not bad at all...qualifies you for the A32x series and anything below).
Do you know if FlyUk allows transferring hours on their website?
The airline he is transferring hours from has no say in the matter really, as long as the hours can be viewed on their website. Or did I misunderstand and you are actually asking if they will accept your Metro hours were you to join them? In that case, they do accept previous VA hours but they do not count towards your rank, they are only there for display and I suppose your own record keeping purposes.