Perhaps a family rail card would help?
Rail comes into its own for longer runs, I find. For instance, Llandudno to London can be done for about £80.00 for two. In a car, although the fuel might cost less, you have to add in depreciation, insurance and maintenance as well as the stress of driving down to London and finding somewhere to park as centrally as the train delivers you.
We go to Europe fairly frequently and would choose Virgin to London and Eurostar after that every time. Not only is it a much more pleasant experience on the train in terms of getting to your destination, it's largely comparable with flying in cost terms.