Whether it is value for money probably varies from vet to vet and may also depend on whether your dog is insured. We didn't take out the plan at our vets as it seeme quite expensive. Flea and worming treatments can generally be bought online much cheaper than from the vet. By taking two dogs for one vaccination appointment we get a 20% discount on the overall bill for that anyway. At our vets monthly weigh-ins are free, the vet said I can just pop the dogs in any time. The plan offers 10% off any treatment, but as we have insurance anyway, this is not really a selling point.
I think you will need to add up what is included in the plan and consider whether you would use everything to see if it is worth taking out. For flea and worming treatment see websites like VetUK.