You description of the discs sounds a little odd. Are they commercial DVD-Video discs with a Region 2 symbol on the box etc?
Assuming these are normal WH Smith-type discs....I can imagine that with the multitude of combinations of hardware and software combinations that you could find on a PC/laptop, it's possible to run into problems playing the discs. But I would expect any consumer DVD player attached to a TV to play them without problem.
Do any of the players that won't play them give you any type of error message? My DVD player displays a message saying the disc has an invalid region code if I try discs bought in odd places.
If they're normal DVD-Video and won't play in a consumer DVD player I would take them back 'cos they're broke.
On the computer, have you tried any of the software that ignores some of the superfluous stuff that you might get on the discs from some companies - maybe VLC player or (my personal favourite) MPC-BE?