Digital UK came under the Freeview banner from Nov 2019 which was not a positive development actually but this page has some useful info / links.

tx.mb21.co.uk : TV and Radio transmission and reception site including :
“Transmitter Gallery”, Transmitter maps and "All the transmitters" (this fabulous comprehensive interactive map may take some time to load ! ).

wrightsaerials.tv : The second best aerials website in the country, and it's also based in Sheffield !

bbc.co.uk/reception : BBC reception advice website, includes a basic reception predictor for TV, DAB, FM, MW & LW (but, basically, the site isn't as good as it used to be.....)
Also see :
Transmitter Reminiscences
BBC Research & Development Reports (full list of)
bbceng.info  :BBC engineering from 1922 to 1997. Give that man (Martin Ellen) a medal.

ukfree.tv/transmitters/locations/Freeview : UK Free TV, all the Freeview transmitters in alphabetical order

screenonline.org.uk : Colour Television Chronology

arqiva.com : Terrestrial transmission page of “arquiva” (spx). They bought out the transmission arm of NTL, who bought the ex ITV (IBA) transmitters in 1997. Arqiva bought out National Grid Wireless in Sept 2009.
As an aside, National Grid Wireless were the other half of the privatised transmission networks (the ex BBC transmitters) but sold out to Arquiva [sic] in Sept 2009. NGW had themselves bought out Crown Castle in 2004. Crown Castle originally purchased that half of the transmission network when it was privatised in 1997.

wolfbane.com/articles/tvr  : Wolfbane's UK TV reception page. Very useful links / resources page, but note that the reception predictor can be a bit pessimistic !

R Book (8) : UK Digital Television guide (July 22)

barb.co.uk : B.A.R.B (TV programme viewing figures)

radioguide.co.uk : Radio Listeners Guide and Television Viewers Guide.

gridwatch.co.uk : Where our electricity comes from.....

pylons.org : And how it gets to your house / work......

ukphoneinfo.com : Very handy site telling you which area codes and 5 figure numbers.

canalworld.net : Canal World (Forum)

keepbritaintidy.org : Keep Britain Tidy........ (there's a clue in the name)

20splentyforsheffield.org.uk : Though even 20mph is too fast for the road I live on…..

bing.com/maps : Bing maps = Ordnance Survey (the original, and the best)

Historical maps (National Library of Scotland)
Sabre historical UK maps 7th series 1" maps
Sabre historical UK maps sheet finder
History of the Great North Rd (Sabre thread) (incl many historical map links)
Geograph (set on Smithywood)

ukmotorwayarchive.org.uk : Everything about motorways, including all the openings. As I've got a bit older I`ve rather gone off driving (too many cars on the road, of which far too many are driven by aggressive wazzocks), but this site is fascinating, particularly for those of us with a slightly autistic interest in dates. Also see roads.org, and Sabre road network changes (set for the 1960s).

brake.org.uk : “Brake” the road safety charity.
Be careful on the roads, they`re dangerous.
Better 10 minutes late in this life..................
....................than 10 years early in the next.

streetmap.co.uk : Converting grid references to postcodes etc

metoffice.gov.uk/research/climate/maps-and-data/uk-temperature-rainfall-and-sunshine-anomaly-graphs : Met Office UK weather anomalies.

saynoto0870.com : Marvellous site telling you how much of a “Rip Off” 0870 numbers are and how you can sometimes get round them.

confusedaboutenergy.co.uk : Ahh ! So electricity can be cheaper than bottled gas !

noiseabatementsociety.com : “Keep it down old son......”

railrovers.org.uk : Get out, and explore !

(Building) 6207 A Study in Steel : To be frank I'm not a big You Tube fan, but for anyone with the slightest interest in engineering or railways, this film of the building from scratch of a Princess Royal class steam loco is fantastic.

Database of (main) OHL electrifications in the UK (Jun 21)