Hi Joe
I would not be investing in a pension fund if I was getting only 20% tax relief.
You will not be able to access your money until your retirement.
You may be paying high fund management charges.
Tax relief is really tax deferred. If your pension brings you into the higher tax bracket when you retire, then you may be saving 20% now, to pay 42% tax on it later.
Save the money in some other low cost unit-linked fund or use it towards paying down your mortgage if you have one. If increases in your income bring you into the 42% bracket again in future years, transfer the money from your personal savings into your pension contribution until you have used up your 42% tax band.
Brendan