Am not sure what you mean when you say you will get taxed on your pension. Yes, you will get taxed on your pension when you draw it in 35 years time, but in the meantime, while you're contributing, you get tax relief on all your pension contributions. The fact that your company is matching your contributions seems too good an opportunity to miss. Gordon Brown certainly won't be matching your savings into an ISA.
I assume you mean an ISA account (not ICA) as an alternative? There's no guarantee that ISA's will be around after the 2009/10 tax year so they may be a short term investment for you and there's always the temptation that you will want to cash it in before you retire. In your age group I think a good pension fund pot is going to be absolutely essential to living a comfortable retirement. At 30 you may well feel that 65 is so far away in the distant future that it's not worth worrying about. Believe me, it will creep up on you faster than you imagined, and as you grow older, knowing that you have the backing of a good pension scheme will make your ageing years feel a lot more comfortable.