Most insurers will provide cover for shorter periods of time, alternatively, you could just cancel it when you do not need it. I am assuming you declare the vehicle SORN when you go away, so do not need to have it continuously insured. If you do tax it, then you would need to keep it insured, so make sure you cancel the tax. I would suggest you still insure it whilst in your garage though, and some insurers will cover this for you. (Storage cover only).
Alternatively, there are new insurance products like CUVVA www.cuvva.com/ and Pay By Mile www.bymiles.co.uk or Coverbox www.coverbox.co.uk/pay-as-you-drive-insurance that will give you the best of both worlds. Where you only pay for insurance while using the vehicle, though it still insures the vehicle when not in use.