i cant believe folks still have limited connections and are happy with that!
my own opinion bearing in mind I have no idea what land line deal you have is to have a look at the wider offerings available out there as an example
sky offer an 18 month contract on ADSL which includes line rental at £18.00 a month this increases after the 18 months to 38.00 but you also get a £100.00 prepaid card into the deal so with the card thats just over 12.00 a month granted no calls included but you can pay a small fee to have all that added personally my Wife and I have included calls on our mobiles so a landline is never even plugged in.
I left Zen for Sky and was happy for 5 years brilliant service and connection previously i was with Zen for 6 years, have just left Sky for BT on a FTTP offer.
Seriously look around dont get stuck on just one ISP because of a perceived Quality of service offer truth is all isps are pretty good these days.