What is "acceptable" non-fibre Broadband speed?

Hi all, I have been with a big name provider for good 6 months and consistently get around 7-8meg download speed, and around 0.90mb up. It is not fibre, they just installed an OpenReach Mastersocket 5c. If a movie is streaming at non-HD res then no one can use their mobile for things like Twitter videos or even pictures. Is there anything I can do to ask them to improve it? I do not want to pay the extra/new contract for fibre really as possibly will go with another after the contract runs out.

Thanks!