A one hour boil which is necessary to clear the beer of some of the excess proteins will remove any chlorine. It will not remove fluorine as this is present as fluoride.
Sheffield tap water’s fine though may be a bit soft. You might want to try adding gypsum to your brew liquor at the rate of about one desert spoon to every 10 litres. This is what makes Burton Water the ideal water for brewing. This should stabilise the Ph prior to pitching at about 5.2.
Forget bottled water, different makes contain different minerals and, unless you’re into chemistry you’ll have no control over your brew. Besides, it’s dearer than beer!
Take Fezzyboy’s suggestion about Bradfield Brewery seriously. They do excellent beers in sizes suitable for the home. I also believe they now have beers available in bottle. Get to know what real beers taste like and get to know the brewers. Most head brewers I know are dedicated to their job and will talk for hours on the subject. I don’t know the current situation, but when I was brewing in the 70’s you could not get a decent top fermenting yeast. (You could not get a decent bottom fermenting lager yeast either, but that’s a different story). Knowing the brewers will enable you to cadge the best strains of yeast. I used to get mine from Whitbread at Lady’s Bridge.
If the brew shops in Sheffield are still in the hands of the same family then you will also get good advice from them. I knew Colin, the father of home brew in Sheffield back in the 70’s and 80’s when he had a stall in the market and his son ran the shops. If they didn’t know the answer to you problem, they would always find out.
All the best