If I have a private pension scheme from previous employers can I just transfer the old contributions into the new scheme?
Yes, you can usually do that without any great hassle. Duuno about BA, but I'm pretty sure Virgin will contribute directly to an alternative pension provider if you do all the legwork. I seem to remember that the only disadvantage was that your contributions weren't net of 40% tax at source, so you had to claim the difference on your tax return. Mind you, it's a while since I investigated this, so that info may be well out of date by now.