This may be a good starting point - it wll give you an idea of costs.
I don't believe in life assurance / insurance as such. You can get very little return for your money - and at your age you will hopefully be paying in for 30 years or more!
If you only want to make sure your funeral costs are covered, there are other options.
You can pre-pay your funeral in instalments or a lump sum now. That means that the funeral will be paid for at today's prices and you have control over the type of funeral it is.
But I would recommend you open a deposit account that pays good interest, and save regularly. As a tax payer, an ISA may be the answer.
Funerals can cost as much as you like, but �2500 is a realistic amount.