30 years? What sort of crystal ball(s) do you think we have here!?
The Virgin pension scheme is run through Scottish Equitable. If you leave them to make all the investment decisions, you can expect something less than the market average rate of return on your investment. If you take the opportunity to take some control of the investments yourself, you can improve on that considerably - or you could lose the lot!
Virgin will pay a contribution of 15% of basic and variable pay, as long as you contribute at least 6%. Until age 51, by legislation, the most you can contribute is a total of 30%, so your maximum individual contribution until that age is 15%. Above 51, through changing to a personal pension within the scheme rather than the group pension fund, you can increase that total each year as you get older.
If you contribute at the maximum rate, achieve command at (say) 10 years, and your career last 30 years, and stay within the group scheme, your fund (at 2005 pay rates and a compound growth of 5%) will be something in the order of the proposed maximum allowed fund of £1.7m (I make it just under that figure). That would give you a pension, at current rates (and using very simple options and no extras) of around £70k pa.
Of course, such a calculation is fraught with 'what if...' and 'but...' errors. You could do better than this figure, you could do worse.