fixed rate or tracker in this climate

Hi
I bought a property two years ago.
My mortgage is due for renewal in Feb 2013. My current lender (Natwest) has sent me a letter with the instructions to check their current deals online with £150 cashback offer if I renew it online.

My remaining balance: 91,918.11
Term: 23 years 6 months
Repayment type: Capital and interest

I have logged into their website and I am being offered following deals;

1- 2 years fixed mortgage on 3.35% rate with £995 fee
2- 2 years fixed mortgage on 3.59% rate with no fee
3- 5 years fixed mortgage on 4.09% rate with no fee
4- 2 years tracker mortgage on 3.59% rate with no fee

I have bought this property on home buy direct scheme (15% by developer and 15% by government). I was told that only limited lenders can offer me mortgages.

Considering that and considering offers above, which one is better for me?

Also would I benefit by going to mortgage advisor? Can I get deals better than the deals mentioned above considering that property is home buy direct property?