I have the lowest level with VM and I can get 24. I think VM have also said that they will be increasing the speed at no extra cost.
Why would anyone pay for the highest speed, when if you read the small print there is no guarantee ?
You might as well phone VM and change your broadband to a lesser speed, so you pay less, but will probably get the same speed as you have been experiencing.
Your experience is unlikely to change by moving provider. It depends on a number of factors e.g how many people are using your local nearest exchange/hub and the speed of internet site servers.
It is a bit like buying a Ferrari which can do 200mph and being restricted to 50mph due to traffic, speed limits etc. Downgrade your service to what the network is likely to be able to provide.