Tipping in London

Yes, only tip for something unusual (that is, do not tip 2 out of 3 times), and only ever tip restaurants and taxis.
You may find this hard, but, please restrain your tipping addiction :-)

Theatre ushers?

They aren't tipped in the US, but I remember that guide books used to say to tip them in Europe, or at least in some countries in Europe.

but I remember that guide books used to say to tip them in Europe

Who writes these guide books? US-Americans write them for for US-Americans. It is like a drug addiction (or toilet training). I have been taught from an early age that you must tip, it is ingrained into my subconscious, and my brain cannot conceive of not tipping without risk of a cerebral implosion. :-)
(please accept the above was written in a light-hearted manner).

I have never tipped a theater usher while attending a Broadway show.

My information may be wildly outdated, but I'm certain such statements did appear in guidebooks. And those guidebooks acknowledged that we do not tip ushers in the US, so they were not (in this particular case) projecting US attitudes onto European situations.

The practice may have been limited to just a country or two, or it may have changed.

In London, many restaurants will automatically add a 12.5% "discretionary" service charge to your bill. Technically, you can ask for it to be removed, I always just pay it, but I don't add anything beyond that,

My experience in restaurants on multiple trips, mostly London, is that for self service (order at a counter, they bring you the food) no tip is required. This includes Pubs when you sit in the bar, even if you order a full meal. At sit-down, full service restaurants, some payment for service is expected, especially in more touristed areas and higher end places. As was mentioned, sometimes the service charge is added or it is specifically noted that service was not included. Tip based on quality of service, 10% is plenty fine for better than "good" service, go up or down from there, but no need to do the 20-25% some people feel is necessary in the US.

Other than that, I do not recall tipping in many other instances, maybe rounding up for a cab or adding a bit, tipping a tour guide a couple pounds, but not much else.

In full-service restaurants in the U.K., its traditional to tip around 10 - 12.5% if the service has been decent. BUT in London (and a few other places) you may note that a service charge of 10 or 12.5% has already been added to your bill, and in this case there is no need to tip any extra.

You don't generally tip in cafes or pubs* where you order food/drink at a counter although there may be a tip jar at the counter if you want to give something.

*if it's a restaurant within a pub, with full service, then restaurant rules will apply.

In black cabs, I usually round up to the nearest pound - if it's an £7.50 fare I might give the driver a ten pound note and say "take 8 from that."

I've noted that even outside of London, tour guides have started pitching for tips. I did a boat trip on the River Dart which was already quite pricey, and the tour guide pitched for tips at the end, but I chose to presume his pitch was only aimed at Americans and ignored the cap in which he was collecting coins.

"In London, many restaurants will automatically add a 12.5% "discretionary" service charge to your bill. Technically, you can ask for it to be removed, I always just pay it,"

Surely you wouldn't pay it for bad service?

The tipping ushers question, they used to do that in France, not sure if that's still the custom though.

Courtesy of TA:
https://www.tripadvisor.co.uk/Travel-g186216-s606/United-Kingdom:Tipping.And.Etiquette.html

Always remember that you DON'T HAVE TO TIP.

Tipping falls somewhere in between the USA/Canada and Continental Europe practice, but increasingly leaning towards the latter. It is also rather different (ie more prevalent) in London than elsewhere in the UK.

In more casual restaurants tipping had largely gone out of fashion - it seems to be the restaurant trade in the main that tries to keep it alive. Still many people discretely hand over a pound or two when paying the bill

Decline 'discretionary' service charges at restaurants and give the server what you think he/she deserves - and will get rather in nearly all cases rather than going through the sausage machine of the management.

HMRC thinks that the average tip received by a taxi driver to be 9%. It is however more common in London than elsewhere where tips seem a pleasant surprise.

No need to tip bar staff / hairdressers / barbers / usher(ette)s etc. Porters a pound or two if carrying something heavy maybe.

Don't tip policemen :)

In France, it used to be the custom to tip ushers in movie theaters. It was also the custom, in the U.S., to tip ushers at baseball games.

I've noticed tip jars everywhere in Europe now and many credit card receipts, in restaurants, pubs, etc., to now have a line to add a tip.

I pretty much follow what most of the natives do when in the UK: round up in a taxi, 10-15% in a full service restaurant, but never in a pub, cafe, barbershop.

I've always wondered about local guides. I've taken numerous London Walks...walks....but never tipped.

The strangest place I actually saw a guide put his hand out for a tip was the Yeoman Warder at the Tower of London. When his tour was over, we all walked passed him to get outside and he had his hand out, palm up. Not a signal he wants to shake hands but that he was expecting a tip. (This was a long, long time ago.)

Thanks all for the advice!!

Thanks all for the advice!!