I'm told that is the profile from the tap and not softened (and that the report is dated) alkalinity is more like 280ppm.
This is getting into the 'make me nervous' range for bicarbonate. I think a gypsum addition to up the Ca and SO4 sounds good.
But am concerned, in How to Brew, Palmer says 'The combination of sodium with a high concentration of sulfate ions will generate a very harsh bitterness. Therefore keep at least one or the other as low as possible, preferably the sodium."
Beersmith's London profile is:
Calcium(Ca): 52.0 ppm
Magnesium(Mg): 16.0 ppm
Sodium(Na): 99.0 ppm
Sulfate(SO4): 77.0 ppm
Bicarbonate(HCO3): 156.0 ppm
PH: 8.0 PH
I was thinking I'd come as close to this as possible as the brew has a high % of English malt.
I've been following ajdelanges primer with great success. I am going to testmash (I aways forget it's this simple!) and adjust pH using lactic acid.
The best beer I ever made was the next one I brew.