Drives me round the U-bend....

Getting ripped off by tradesmen. How can we avoid it? Recently I needed a plumber to do what turned out to be a rather awkward job fixing a leak in my U bend, toilet flush pipe and soil pipe. We weren't sure which of these it was so decided to have the whole lot replaced so that, hopefully, we would never need to have any further work done. The tricky bit was that it was one of those concealed unit type cisterns, the ones which were particularly popular in the 1970's and 80's designs. Why was that? Did they perhaps think that some how a normal, obvious-looking toilet cistern ceramic box was a little unsightly or something? Anyway my usual plumber was called in, I won't name him here, well maybe I will later! He gave us a figure of £200 and I swear he said "up to" that amount, so was obviously expecting to pay about that, hopefully a bit under. Now I know that plumbers, plasterers etc. are in demand at the moment, but I thought that he wouldn't need reminding any more than 2 or 3 times to come along and actually carry out the job. Oh no, 7 or 8 phone calls and a chance meeting outside Somerfield at York Parade later and still no plumber. He had said the job wasn't urgent since it was probably only the flush pipe leaking fresh water slowly onto the top of the U-bend; I had by this time put a sponge in a bag to catch and soak up the water (a rather ingeneous solution, even though I say so myself, but only ever a very temporary measure.) So, nearly five months went by before I eventually pleaded with him to come around and do the job because the leak had got worse, I little bit of a white lie, but it did the trick! He turned up a hour late on the arranged day, took nine hours to not quite finish the job, left us with two dirty great holes in the cistern plaster board casing and said we'd have to leave it two weeks to let the flooring thoroughly dry out. He'd been there so long that, and it was Maundy Thursday evening, he said he'd have to work out the bill and let us know. Fair enough, I thought. About a week later I nearly fell off my chair when I received his invoice for £490.01 (let's not forget the penny!) To cut a very long story short I sent him a letter pointing out that it he had said it would be up to £200 and not two and a half times that amount; in any case he hadn't fixed in the flush button, nor had he made good the job ie fixed the pannelling and holes in the partitioning back on. It seems that the law on this is somewhat ambiguous; on the one hand his final bill shouldn't be unreasonably higher than his estimate, but on the other it depends on whether his job has been up to scratch and whether it reflects the true amount of time he spent doing the job. So what is the worth of any kind of estimate, if he can then just charge whatever he likes and claim that verbal estimates are not accurate? Any lawyers out there, feel free to help me out on this one! In this case I knew that the job needed finishing, I thought that I needed to pay him to avoid any legal wranglings, so compromised on him coming in, finishing the work and refixing the damage (he had made) for no extra charge. I am left with mixed feelings; was I ripped off? I certainly don't feel completely satisfied with a job wells done, but at least the job is done and hasn't been left messy. All's wells that ends Wells, maybe....