Hi Gav,
As .tel domains are mainly intended for contact details the main thing I would register is first/last names as I suppose they could prove popular in the longer term.
If you have bought a surname that is also a trademarked term you should be fine unless you did something stupid such as filling your page up with affiliate links to the TM holders competitors for example.
My main advice though is don't believe the hype - you're much much much better off spending your money on good .co.uk domains, either by picking stuff up for reg fee or searching these forums for bargains in the sale sections, if you can't sell them then at least you have the option of putting websites on them which you cant with .tel.
There are also shed loads of good .org.uk/.me.uk domains available which you could potentially earn a living from if you can develop them into decent sites.
Grant