OK, I know this a 'how-long-is-a-piece-of-string' type question, but a guide would be useful. I rent out a flat which has a ten-year-old Ravenheat combi boiler in it. Over the past couple of years it's started playing up. I've had a few jobs done on it but the costs are starting to rack up. I'm therefore thinking of getting it replaced. I'm thinking a new Vaillant combi which will presumably need a new flu and the pipework re-jigged a bit to make it fit. What's the consensus from the Screwfix wise regarding the cost of a job like this? Do most plumbers treat these things as a two-man job? (The reason I ask is that since I installed the system originally I'd be happy to be the second man - wire-wooling joints ready to solder etc. etc. just to speed things along and save some cash). Any thoughts gratefully accepted.