The problem with this water is its alkalinity at 2.72 mEq/L (as CaCO3/50). Accompanying calcium is 1.74 mEq/L. If you supplement calcium to say, 3, then you would be able to, theoretically, get alkalinity down to 1 mEq/L (by boiling or lime treatment) and still have calcium at 1.28 which would be OK for many beers. With the low sulfate and chloride clearly you have plenty of headroom for addition of the extra calcium via the chloride or sulfate salts.
Clearly just adding gypsum and calcium chloride isn't going to get you there as, with a nominal pale ale grist formulation and a 5 gal brew length you would need 30 grams of each or about 10 grams per gallon of each. The nominal recommendation for these salts is half a gram per gallon.
Sauermalz is a possibility but, assuming a target pH of 5.4, a mash thickness of 1.5 qt/lb, 85% pale ale malt and 10% crystal 5% sauermalz would be required. That's getting up there and not exactly traditional for pale ales.
You could also use lactic acid but, again, it will take quite a bit, nominally 6.2 mL of 88% strength solution. Again probably OK but perhaps pushing it a bit and also, once again, not very traditional.
65 mL of (readily available) 10% phosphoric acid might be a better bet as it is flavor neutral but best of all would be 19 mL of AMS/CRS which would not only knock out the alkalinity but bring your chloride and sulfate up into more reasonable range and be very traditional for UK style beers. Unfortunately you can't (AFAIK) get the stuff outside the UK. Given that your long term best option would be to install an RO system and in the interim soldier on with lactic or phosphoric acid.