Ideally you should be heating your boiler up to above 60 once a month in order to achieve a legionella kill. Above 50 prevents growth but won't likely deliver you a kill.

You can measure that temp at sentinel outlets though - nominally the first outlet on the flow from the boiler...and checking out the last outlet will give you a good idea of whether you're getting full circulation at that temperature.
So a temp gauge can make life easier but isn't by any means a requirement so long as you can demo in other ways.
Which brings us on to mixer valves....an oft held debate. Unless your satellite office employs vulnerable people then scalding is rarely a genuine risk. It's more often than not a comfort/complaint issue...and designers do love to incorporate them.
Is there some other means of checking the temperature of the pipes? Can you access and use a surface probe on the pipe itself to check temp of water inside? How much of a hassle is this?

And therein lies your debate - hassle of checking circulation temp as an indirect measurement of boiler temp vs getting a gauge.



Additionally, unless your showers are infrequently used, you could probably get away with disinfecting/descaling on a quarterly basis unless you've got some other issues on site.

I was actually thinking of mentioning your point Chris. ;) Not that I knew about it until you raised it on another legionella related thread a few months ago....


But most mixer taps or TVC's still deliver at above 40C - presumably based upon the misplaced fear of scalding rather than anything else. Luckily in an office, chemical uptake risks are likely lower than elsewhere but the point is still well made about the how and why of mixer taps being installed is seemingly removed from the relevant science.
I note that HSG274 Part 2 expects them to deliver temperatures between 38 and 46 and suggests that the fitting of them is a trade off between scalding and risk of legionella. I can't thus see that they serve any genuine h/s function in an office environment but I struggle to think of many dedicated office sites built in the last ten years that haven't installed them almost as standard. It leaves people like Zanshin having to make other compromises as a consequence...let alone your point about skin damage and increased associated risks!