D Seth
I am afraid I do not agree that you can achieve your goals without taking the risk involved with investing in the stock market /property- - "I would like to keep the money"
Fairly liquid
Beat Inflation
Achieve Growth
Take Income
Stock markets do go up and down and one only has to realise that the UK is still 10% off its peak of 10 years ago and Japan is still 70% off its peak of 20 years ago.
With a bank rate of 0.5% and inflation of around 3% in UK putting the money in a bank (ie. liquid) will not match inflation over long term never mind tax. Bonds everyone says are too high and once Quantative Easing stops so will they. Shares have rocketed up in past month so are due a small correction.
If you have never invested money in shares and or bonds a do it yourself approach is doomed to cause worry and probable failure - you should not start investing as a first timer with £750k.
I would split it into 3 parts of £250,000
1. Buy a flat in London, or Oxford or Manchester or Leeds (big city with lots of professionals and studenst wanting to rent. Pay an agent their 15-17% and use the income after tax to provide you with yours Income and look for increase growth in the flat's value. Do not by a cheap and nasty lace because it will not go up in value - buy one a Phd Student or young professional would want near the centre of town.
2. Go to a company like Best Invest (they use Fidelity's co funds for investments) and get them to look after your £250 k - OK they charge but if they don't beat an agreed benchmark over 5 years then move to somone esle later.
3. Buy with the last 250 K - £30,000 worth of premium bonds for yourself, your partner, your mother, your brother, sister, cousin, your dog (joke). If you are married or have a partner /children make sure you buy insurance to look after them if something happens to you (e.eg a sign falling on your head ora heleicopter falling out of the sky) and then put the rest into bank/building society accounts but not more than £85,000 in a\ny one. Drip feed money you don't need to keep Liquid in the bank into bonds through a specialist bond dealer.
Good luck I wish I had your problem
Phil