Plumbing variation

I have completed a owner build at home. Plumber gave me a quote. I told him in the day that there will be a couple of extra things that I would like done like capping some gutters and a new flashing at the back of the build. I then received an invoice for nearly 3 times the amount of his quote but there was no mention of variation quote, time frame approx or costings approx. he was telling me its a verbal agreement and he charges accordingly. I have asked him for an itemised invoiced but have received nothing back and it been a week now. On this invoice there was also a lot of other stuff that was done like pointing and flashings that should of been on his original quote as it was an extension him being the professional should of known this. Do I have any leg to stand on here. I happy to pay him at least 75% of it but not all of it.