In my National Rail timetable, 1999 - 2000, those are tables 352 and 353, and are headed "Proposed services only. These planned regional Eurostar services are subject to review."

I did finally find a report about the schedules - from the Aberdeen Press and Journal 09 June 1999 (well, why not?). Headed "Ghost trains hold up services", it refers to the two empty paths from Manchester and one from Glasgow, and says "A Wolverhampton-Coventry service is held up for eight minutes every weekday from 8.01 to allow the non-existent Eurostar train to pas through the station."

The factual bit at the end says "When Eurostar first reserved the lines for these trains, it expected that regional services would be running soon. The company has since had to pay to keep the lines open in case the regional service becomes a viable proposition when the much-delayed high-speed link from London to the Channel tunnel is finally completed."

IIRC^▸ (if I recall/remember/read correctly) the NightStar stock was sold to the Canadians in 2000

I think the credit for the day and night services is probably more due to BR^▸ (British Rail(ways)) than the UK^▸ (United Kingdom) Government, but indeed, it was arguably an attempt to make the
Channel Tunnel 'relevant' to the country beyond London.

Their failure was largely down to privatisation, which took them from being financially dubious, but sustainable within the broader BR entity, to insanely expensive as standalone services, and very visibly so, as they would probably have needed a heavy subsidy.

There's also the question of how well the 373's would have worked out technically beyond London (GNER^▸ (Great North Eastern Railways) did have them for Leeds services, but they were highly restricted in terms of route) and whether the customs/immigration issues would have worked out.

And then there's the question of how long a trip like Manchester to Paris would have taken, crawling round the West London line then across Kent on third rail. Remember also that the budget carriers like EasyJet and Ryanair were starting to make inroads at the time.

Don't forget also the security concerns of the time - the Channel Tunnel was felt to be a prime target for the IRA, and I'm sure that the security services would have been concerned that the 'north of London' services posed a soft target.

All that said, it is very interesting to ponder what might have happened had work on HS1^▸ (High Speed line 1 - St Pancras to Channel Tunnel) started earlier and BR's privatisation been put off a few years. Would HS1 with a decent connection to the ECML^▸ (East Coast Main Line) and WCML^▸ (West Coast Main Line) have made Birmingham/Manchester/Leeds services credible, and would that have created momentum to build new HS^▸ (High Speed (short for HSS^▸ (High Speed Services) High Speed Services)) lines north of London rather than upgrade the WCML?

Of course the other Eurotunnel question is if BR's privatisation had not taken place, might it have been the saviour of wagonload freight? But that's another matter :-)