In a past thread(s) I've put the long list of reasons against reels & dug this one out:
"Reels are very suited to warehouses, industry & large open spaces, but in offices we find the following:
1) Most reels are not boosted and do not meet flow rate requirements
2) The location of many reels requires them to be run through fire doors, including those onto protected routes & through protected lobbies, thus rendering compartmentation useless
3) People leaving & fire fighters entering can trip over them
4) Despite the impression on training films most reels require two people, one on the drum, one with the hose, even where the reel is annually serviced (which often just entails seeing if water comes out & if you are VERY lucky a flow test on the highest reel)
5) They have an unlimited supply with the risk of staff doing a "towering inferno" & fighting the fire longer than appropriate
6) The most likely source of origin of fire in a modern office is likely to be electrical - water being shot about at 30l/min isn't really helpful
7) They do leak from time to time and are expensive to maintain adequately, more than once they've caused floods"
Add to that water hygiene issues with water stood stagnant in a warm building for long periods of time.
s20 is no longer a barrier to reel removal (they could always be exempted from being provided under s144 by the BCO anyway) and several London buildings have removed them - as long as you can justify it in an FRA you won't often get an objection.