Well, you have an engineer coming next week, so there's hope!
I wonder how many people are sharing your line? Perhaps the engineer may switch you onto a better line?
I have Virgin cable, and the engineers are wonderful! And Virgin don't charge for visits or replacement equipment - I had some niggles with the Superhub when it first came out - they don't repair, they just put in a new one. I actually have a spare, which I'll give back next visit! I've been upgraded to 100mb, and all the speed tests show about 97-98 mb!
Sorry if you're not in a cable area.
If all else fails, Sky would be a better bet, and there are some good deals around at the moment.