Leigh exchange apparently has SDSL?
Convert the ADSL to SDSL and you'll get 2mbit upload on both lines - get the lines bundled together and you'll have 4mbit up/down? You'll be looking at ~£600/mo + setup & hardware
But for that you might as well get a leased line in:
Etherway 100Mb/s fibre
Internet Etherflow 10Mb/s £3,062.00 £815.00 £9,780.00
That way the office is on a 100Meg bearer, and you can upgrade to more bandwidth if required..