Classify yourself as a retail (not professional) investor if you have a choice. That way you get the highest level of protection. Your broker may default you to professional so they have less risk.
Capital Gains Tax (CGT) will be reduced to a 18% flat rate from 2008-9 tax year. The first £9200 of gains in tax free. CGT is a separate tax, and your salaried income is not considered.
The bank should automatically deduct tax from your account otherwise this will have to be paid later.
You can put pre tax money into a pension. Maybe this cuts down on employer NICs, employee NICs and income tax.
At retirement, you can take 25% out (is it tax free?). and with the remaining 75% you must buy an annuity.
You pay the remaining 75%to pension company and it will pay your a fixed income every year until you die. e.g. At age 65 you have 100K remaining. You give that to a pension company. They will pay you 8K per year until you die. Not sure what happens with interest rate changes, if the pension company goes bankrupt, and why can't I manage the payouts myself. Its as if these rules state that everyone is incapable of managing their income.
The income you receive from the annuity is taxable income.
There maybe an alternative called Unsecured Pension.. need to research this.