As you say you do not want to take any risks then a cash Isa is the best and only option. Look at the best buys in Moneywise and consider whether you wish to tie the money up for a fixed period or whether you wish to have immediate access at all times. Immediate access will usually mean a slightly lower rate.Max 3600 pounds this tax year. Perhaps the balance could be put into an Internet immediate access account which usually have better rates than those on the high street.This account will have 20% tax deducted at source but if you are a non tax payer you can ask them to pay the interest gross by completing an appropriate form when you open the account.

 As you did mention pensions I would make one or two points for future reference in case you do decide to start one. Not risk free but you would be looking at long term savings so the risk aspect is not really a factor.The tax relief is also important. 80 pounds premium for example means an extra 20 pounds tax relief for non and basic rate tax payers being added by the Government. You say you are a single mum and any decision to start a pension must also depend on your projected earnings and career/work prospects.If you anticipate low future earnings and a fairly intermittent working life then you may only be able to build up a small pension fund.You will not be able to draw a pension until age 55 and pension then would be reduced considerably by taking it at such a relatively young age. What I am getting at is if for example you built up a fund of say only 100,000 pounds by age 65 this would at the moment only give you a pension of around 4000 pounds a year, increasing with inflation. If in the future you were going to be considered for pension credit then this pension may be taken into account when they assess you and you may find you have made the contributions and sacrifice for nothing over many years. Problem is noone knows what the benefit system will be in 40 years time and what criteria will be used nor do we know what a pension fund of say 100000 is likely to pay you. Speak to an independent financial adviser if you want to consider this in the future but be careful if you really cannot see yourself being able to put much into the pension over your lifetime.

If you are anticipating a long working career on reasonable income I would consider a pension at an early stage.