Loft Insulation Advice

[Collinsc]

Hi

I would appreciate some advice on loft insulation. I moved into my property about 4 months ago. It is a first floor 2bed flat, built in the 70s.

The insulation is virtually non existent. I had a company come round the other day to ask for advice (as part of the government initiative) - though i intend to do it myself - i was just getting their expertise.

The requirements are:
56Metre squared.
250mm to be fitted.
150 between the joists and then 100mm across the joints.
Distance between joists is 570MM

My questions are:
1. How many rolls will i need? I notice focus are doing a 3 for 1 deal at the moment.

2. There is currently no ventilation up there. The guys suggested having some "tile vents" or "suffit vents" fitted. Is this definitely needed? Which would be best? How much would it cost?

3. I asked about boarding given that the suggestion was to layer across the joists. He said that it might be possible but that would push the insulation down - and make it less efficient. Opinions?

For interest - the quote was £198.

Thanks very much!