London Christmas Lights Bus Tours

I don't know that you'll find an adults-only bus tour but there are a ton of Christmas bus tours out there. Here is one that comes recommended on TripAdvisor, although I can't speak for it myself.

At the very least, it will bump up this thread so maybe someone here on the forum will see it who has taken a similar bus tour. https://www.tripadvisor.com/AttractionProductReview-g186338-d20926219-London_by_Night_Bus_Tour_with_Christmas_Lights_and_Live_Guide-London_England.html

I have seen this one mentioned on the forum, but it does include an afternoon tea:

https://b-bakery.com/london/bus-tours

And i neglected to copy the link for this info., but i copied it directly from the forum and pasted it into my notes:

Later in the afternoon or early evening I'd go on a West End bus (TfL public buses) lights and windows hunt. Sit upstairs and as far to the front as you can get - people will get off and you can move up A bus or a combo the length of Oxford Street, then back and down Regent Street, walk through the Burlington Arcade (be polite to the Beedle), walk around St James's including Pall Mall and St James's Street and the alleys around there for really refined stuff, then back on a bus the length of Piccadilly and along Knightsbridge to Sloane Street. Take in the ethereal lights and decos in Sloane Street, all the way down to Sloane Square (where you can get the tube) or continue west a few streets on Kings Road perhaps as far as Worlds End.
At £1.75 for all the bus you can eat in an hour, maybe 2 or 3 hours - cheap and extremely enjoyable.

The next bus stop down is at Sloane Square, so it’s just a few minute stroll. If you like shopping, the King’s Road there is loaded with cute boutiques. Right on Sloane Square is the beautiful old Peter Jones (now John Lewis) with (at Christmas) their iconic curtain of fairy lights covering the facade.

Nigel mentioned light-viewing from a bus (ideally in the front seats, on-top). I hadn’t seen this thread until now, but he’s right, and we’ve already ridden the Number 14 Bus from Piccadilly Circus to/from the Victoria & Albert Museum, passing Fortnum & Mason, The Ritz, Harrod’s, and countless other displays on buildings and streets. Warmer than being on foot, and traffic slowdowns just give you a better opportunity to view the lights!

Then, the Number 88 bus was the way to see Regent Street angel lights ahead and overhead.
A recent e-mail from The Londonist suggested that the Number 139 bus was the best one for maximum views in London, but not every street would be viewable, including Regent Street. I’m planning on a ride on the 139 when we return next month, while clad in that new long underwear.

We discovered in 2016 that looking at the Christmas lights from the front seats, upstairs, on a bus is the way to go! Warm, eye-level, and you won't get trampled by the crowds or step into traffic while oohing and ahhing :-)