With the big UK banks you will be safe, even though they have had to write off billions they still made profits. On larger amounts Lloyds TSB offers more competitive interest rates. ING direct is a huge bank and for the first year they offer 6%, before it drops. I would not have any issues saving a large lump sum with them.
If you went to a finicial advisor with that sum of money he would recommend investing in the stock market for a higher return over a number of years.
I would also put smaller amounts in some of the high interest easy access accounts as advertised on here. I have 100k spread across 3. I like easy access as you can be sure if you put it in a bond you'll want the money at some point in the year. Also fixed rate bonds with foreign banks, like the bank of Ireland you can not pull your money out during that term. In a UK fixed bond you can, you loose 3 months interest.