How generic is the domain, and if it is, do you intend to use it for its descriptive use? Using apple.co.uk to sell apples or offer information on apples would be fine. If you were to use apple.co.uk to sell portable music devices a certain someone (company) might have issues with it
Do you plan to operate in the same area as the .com? Registered on not, trademarks rights are linked to classes, if you operate outside of these classes you *should be* fine.
Also, you say the .com owner has TM alongside his name, this doesn't mean that he has a registered trademark, here or in the US. It simply means that he is asserting TM rights - he may not have a registered TM anywhere. Most companies who have a registered TM will display the proper ® symbol.
Hope this helps.
P.S. Feel free to PM me the name if you like and I will take a closer look.