If the business is able to get decent ADSL2+ speeds (>15mb) it might be worth speaking to the likes of AAISP or Xilo to find out about multiple ADSL2+ line bonding. Might work out cheaper than £180pm!!
That's something else I'm considering. I did previously get a quote which I can't remember off the top of my head, but it was a lot considering we'd still get slower speeds than fibre. Then again it was from BT so I'm sure I'd get a better price elsewhere. I'll look at two companies you suggested, thanks.
The download speed (14Mbps) we can just about live with. It's the 0.75Mbps upload speed that kills us. Speed tests on 4G regularly reach 62Mbps download and 45Mbps upload here - it's heavenly!