To get UKRA Insurance, you will need to join UKRA, their membership forms are here.
To get BMFA Insurance, you will need to join BMFA, their membership forms are here.

Midland Rocketry also allows the use of the Buddy Scheme, where newcomers can fly at 3 sequential events (eg February, March and April). If there is a break in the sequence (February, March and then May) than you will no be able to fly under the Buddy Insurance and be required to take out UKRA/BMFA insurance (See above links to the respective web sites) before being able to fly at Midland Rocketry.

Midland Rocketry recommends UKRA membership, however if you want more info on which insurance to get, then please contact Midland Rocketry.