The manager who looks after us site engineers allows 15 minutes before the end of shift for cleaning / putting tools away & then washing up / getting changed.

Also as long as the work is getting done on time does it really matter if they take a few extra minutes cleaning up? ? ?

It seems to me this should be the place where the "lead" shop mechanic and/or a shop mechanic that shows some leadership skills should be talked to in private by someone they respect for their actions and not just their job title, and asked if they notice this is being observed and if they think it is really happening or if this was some sort of special thing that was happening. And if they do notice it (or might notice it in the future, now that it was brought to their attention), ASKING [not -telling-] what can they do to help their co-workers deliver that last full man hour of the day. Maybe pointing out that 6 guys taking 10 minutes each is 1/8 of a man/day as part of that conversation.
I think this is a spot were a 'leadership by example' style can have far better results than a 'management by a big stick' style of employee correction.
Road guys ALSO will follow (just not as close or quickly) someone they respect who feels comfortable talking about how they manage their time to bill and actually work and deliver to the customer 8 hours labor each day, and for road guys, a morning coffee and 'lunch box safety meeting' 10 minute round table discussion seems to me to work best as a place to get safety discussions going , give out important company 'news' and get these sorts of discussions -started- with an expectation that the discussion will continue between the road techs for the next few days.

Shop workers = 5 minutes for lunch, 10 minutes before leaving. The extra time at the end of the day is for people wanting to change their clothes.
Road techs = Lord knows what they are up to. :-)

As a service guy for many years, the last thing a customer wants to see is a dirty invoice. I have worked with a couple of "Pig Pens" in my days and if they needed a 15AGC fuse frome their van stock, it usually took them about 45 minutes to find it. If their personal appearance is lacking or their van looks like a homeless encampment, call them on it.

We allow time to clean the area and to put their tools away at the end of the day.
I am strictly referring to personal hygiene- washing up. As I said we use to allow 5 minutes or so but not anymore.

As a shop foreman and service manager I always allowed the tech to bill his washup time to the shop job he was working on and ten minutes or so at the end of the day for putting away tools rolling up hoses or extension cords etc.

Clean up time within reason was always added to the work order, just like putting away your tools. Is this the clean up time your refering to? If you clean up after every job, (Tools put away, van stock items back on the shelf-etc.) That seems reasonable.

Again, I'm not talking about shop clean up time. I'm talking about washing your hands time. In the past we allowed a few minutes to do it but it always gets abused.

It all depends on how big of a mess you've made DuoDeluxe!! Just sweeping up the dust bunnies from blowing off the truck, 5 minutes, running over your oil full oil pan, little longer!

This is for shop techs only. It's pretty hard to monitor road guys.
My experience has been that if we allow 5 minutes for personal clean up before lunch and at the end of the day that the 5 minutes turns into 7 minutes then 10 minutes, then 12 minutes so we are considering cutting it out altogether.

Is this for a shop or road technician? Just like any office personal you should be ready for lunch and quiting time at your perspective time. Clean up is part of the job and I bill it to the customer.