Been there. You get what you pay for, pretty much.
I knew when the children were home from school when I was in Essex and with my old provider, because the 4 meg download dropped to half a meg.
I changed provider. Got 6 meg that dropped to 4 meg.
Up here, I now get 7 meg and it's constant day and night - but I'm with a "premium" ISP because I got fed up with the awful service from the Indian helpdesk I had to use whenever it went wrong.