I had the dilemma of whether to insure or not about 10 months ago - I took out insurance and then cancelled in the cooling off period. I can't insure Artie now as he's over five .... he's also cost me about £1,000 in the time since I cancelled his insurance. a few of those bills have been stasis/bloat episodes costing about £90 - £140, so I would have to pay the first £50 anyway. He had an operation and aftercare costing £336 and a recent stay costing £263 - so, yes, I wish I had had insurance.
My bunnies in the past cost me very little as my non-specialist vet would just give them a couple of jabs and send them home if they were not eating, my rabbit savvy vet does more thorough investigations so costs more.
As Lottielouise says, good plan to get them insured ASAP before they have pre-existing conditions that will become exclusions on the policy.