Service Colonial watch - info sought

Just bought the watch below and whilst I have gleaned a bit of info I wonder if any of you guys have additional knowledge of the brand
The company was founded in Leicester (?) UK in the mid 1920s and sourced the watches from Thiel Bros Thuringa.
There is some info to suggest the cases were made in Switzerland by Tuabert and Fils.The seller states the watch was made for the company by Smiths

The dial logo on this watch appears to have been in use between the 30s and 50s and I have seen a newspaper advert with an endorsement from a BOAC airline pilot in front of a very 1950s plane ( it was suggested it could be a DC4 OR 6). The advert goes on to state that the watches cost between 49 shillings and £7 .There is also mention of an advert with an astronaut endorsement

Most of this info has come from 2 sources who posted a thread on watchuseek in 2010 called Fantasyvoyager from Canada and Mach 1 who states he is from near a Munroe which given my great detective skills suggest Scotland. I am also trying to track them down but they also seemed to be seeking info.

The watch in my opinion is well built and I really like the clean /simple dial.The case is 33mm and is quite chunky but there are no markings on the rear

Any help gratefully received and I will also keep on digging

Dear Vitezi

That is superb thank you very much
I have just spent another couple of hours this morning going through further info and the sites you provided
I love the adverts and am looking to find a dispatch model
It is highly likely that my model has a movement from the Anglo Welsh company who were a joint venture business set up by Ingersoll and Smiths in 1948.
The watch has run for 72 hours and only lost about 1 minute

Cheers
Phil

Memory still functioning

More adverts which evoke a different era and I love the fact that Amy Johnson endorsed the brand along with a man who drove an iconic British steam locomotive

The second advert explains the transport watches come with 2 straps,one for ordinary use and a longer strap for use over your driving attire

The watches were supplied in the 2nd World War to members of the ARP service who were responsible for trying to protect civilians from bombing raids