I manage utility services - among other things - for a group of properties - and have had the mains water analysed for chemical and biological contamination at various times. The results have always been absolutely fine. Not just with EU limits, but far, far, far within them for almost everything and definitely well within them for all measures.
I’ve got no issues at all with drinking tap water in the UK, even given the state of the rivers etc.
In my case, I approached our usual plumbing contractor who have a couple of labs that they usually used. I now go directly to those labs.