Interesting post - I've just taken on a portfolio of contracts which are paying around £12-£13.00 an hour and during the diligence process, I found out that the current cleaning company are charging for all consumables, PPE and equipment. My biggest surprise was that no one was surprised and thought that this was an ordinary way of paying for cleaning.
In respect of the hourly rate of £19.85, and I'm just guessing, this might be the result of TUPE obligations in respect of previous hourly rate, pension entitlement, holidays accrued and/or health benefits. I did a first generation transfer of a cleaner in a school and, to their basic rate of £8.50 an hour, I had an added cost of 21.5% of pension (plus performance guarantee bond) as well as enhanced holiday and sickness entitlements. The resulting cost to the client was round about the figure you're talking about.