The footse index has dropped to around 3800 a couple of times and, in my opinion, it may drop to that area again but wont go further down. If I'm right, it is certainly a good time to buy share based investments at the moment. It's clearly a better time to buy now than six momths ago.
Having said that, my suggestion is that you don't put more money into your existing endowment policy for two reasons. Firstly charges on endowment policies are usually higher than many other types of investment and secondly it is always a good idea to spread your investments between several providers and several investment types if possible.
If you are decided on putting the money into share based investments, you could consider a stocks & shares ISA for the monthly savings and a unit trust or investment trust for the lump sum. You can use the financial magazines at your newsagents and the web sites of providers to decide who you are comfortable dealing with. It's worth looking at the shares that various funds are investing in. I would guess that any fund that avoids luxury retailers, banks and other credit dependent sectors but invests in larger UK companies will outperform the footse index over the next year or two.