I was looking at this a while back and made some notes on trains through Rugby.
I took a specific date (Tue 13th Sep 2022) and found there were 68 freight trains total over 24 hours:
5 car trains (Dagenham - Mossend & return, 2 x Dagenham - Garston + 1 return)
3 construction trains (Tunstead - Park Royal and return + Peak Forest - Bletchley)
2 metals trains (Dollands - Ditton & return Novelis aluminium)
1 possession train (Basford Hall - Leighton Buzzard HOBC)
57 Intermodals
This can be compared with the 1988 freight timetable for Rugby shown in
Freight Only Volume 2: Southern and Central England (Michael Rhodes and Paul Shannon, 1988)
That shows 52 trains for a similar 24-hour period in 1988:
-19 Speedlink
-25 Freightliner
-2 Petroleum (Purfleet - Bromborough Edible Oil & return)
-4 car trains (2x Dagenham - Garston & return)
-2 stone (Peak Forest - Bletchley & return)
Another interesting comparison is that the 1988 freight seems to be more concentrated through the night. If you take the 09:00 to 17:00 period, you get 8 trains in 1988 versus 19 in 2022.
There would also probably have been some local trips / "target" workings for departmental traffic seen at Rugby in 1988 which would not be shown in the timetable. And I'm not including parcels / mail / newspaper trains
Plenty of 1980s footage on YouTube to get a flavour or reminder of the times:
https://www.youtube.com/results?search_query=rugby+1980s+trains
Lineside Video have also uploaded a fair bit of footage from Bletchley circa 1987:
https://www.youtube.com/results?search_query=lineside+video+bletchley
I remember visiting Bletchley a couple of times in the early 1990s and it was a bit disappointing for freight, with the main highlight being the pair of 37s working the RMC hoppers from Peak Forest, as seen here (not my pic):
https://www.flickr.com/photos/httpwwwpeakdaleworkscom/51821720077/
As mentioned above, another big change is the amount of parcels / mail / newspaper trains. I remember a summer canal holiday (probably sometime around 1990-1992) with one night moored up with a view of the line through Weedon on an embankment in the distance. There was a tantalising flurry of mail / sleeper / freightliner trains in the late evening as it was getting dark. I also did a couple of overnights at Crewe circa 1990 and while most of the freight used the avoiding lines, there was enough non-passenger traffic in the form of mail, parcels e.t.c to maintain interest through the night, along with the sleepers (give or take a couple of lulls which allowed a visit to the 24 hour buffet for hot chocolate)...