Just ignore dangermouse46, he has a pathological hatred of british gas, bigburner and heat-line. The irony is that the company he works for owns heat-line. God help him if a heat-line boiler was installed by british gas in bigburners house and he was sent to do a warranty job on it.
The drip may be from a loose condensation pipe inside or the condensation drain may not be running properly. Your best bet is to probably get in contact with your installer followed by contacting heat-line so they can send out a warranty engineer.