It's all back to risk and return. The greater the risk the greater the potential return and potential losses. One of the most basic economic rules.
There are many different types of investment available to you and details such as your tax band, residency status for income tax purposes, whether you are married and your age are all factors which will determine the best tax wrapper (product) to use for your personal circumstances.
Generally, I would look to maximise my ISA allowance, and put the rest into an ISA for the wife. They are simple to get (ISAs not wives) and are almost tax free and you can also get your hands on the money as and when you like. You can simply elect to use some UK equity income funds and take the dividends from the plan (the capital value will also fluctuate depending on the performance of the stock market).
There are also some funds available that are generating between 10-11% returns that effectively act as a factoring service to solicitors. Fairly low risk, but I would only use this for a small (10-25% portion of any income portfolio).
Diversification of the asset allocation is the key to reduce volatility and risk. This does not mean to simply but 5 UK equity funds as they will all invest in Vodafone, BP etc and you could end up with funds that are very similar to each other.
Ask yourself if you need the additional income or whether you would just find it useful. The more you rely on it the less risk you should look to take with it and use cash ISAs and fixed interest or bond/gilt funds within a stocks and shares ISA.
Don't forget that inflation is running at over 5% so any return lower than this is effectively losing you money, but at least you will know that it is only going to be around 1.5-2% in a cash ISA, whereas you could lose up to 40% in stocks and shares.
I would think that you could get professional advice from an IFA, who would get paid via commission, and could sort you out with a portfolio to meet your needs.
Hope you find this helpful.