This story is set around Valentine's Day (February 14th). In those days, a cup replay would take place 3 or 4 days later but daffodils are in view which wouldn't usually be seen until the beginning of March.
Morse steps away from the fashion show to make a call. He puts in his coin and taps the number in. Pay phones in the 1970s were rotary phones, not button.
The insignia (pip and crown) on Chief Superintendent Bright's uniform epaulette is the wrong way round. It should be a crown with a pip below (nearest the shoulder) it but you can clearly see the pip is above the crown.
There are a lot of leaves on the trees for mid February.
'The Striker ' the bike that is being launched is clearly supposed to be a 1970's "Raleigh Chopper", a bike designed with high handlebars and reclining backrest, supposedly based on the American Chopper motorbike, which was fashionable at the time and featured in the films of the day, the most famous being 'Easy Rider'.
The bike being launched however, is the 2004 relaunch version. There is no central gear lever and the struts over the back wheel have a curve in them, whereas the original struts were straight.
The tape cassette used by professor Stamfield carries the brand name 'Archer'. This was a brand of the Tandy Corporation, which did not open their first retail outlet in UK until 1973.
As Morse is running up the stairs in the hotel a upright beam is seen wrapped in LED lights. Not something that would have been around in 1971.