I believe the Peterborough services were going to be 12 carriages (as LNER was reduced to 2tph in the peak), and were reduced to 8 carriages when GTRs new Covid timetable took effect last week.
Platform 10 would have seen the peak Baldock services and off-peak open access.
Looking through it all, the current service plan seems to be as follows.
18 8-car formations in total, 2x365, 26x387, 4x700/0.
In essence, everything is 2x387 with the following exceptions.
2x365
5P05 0604 Peterborough Nene Carriage Sidings to Peterborough ECS
1P05 0637 Peterborough to King's Cross
5E52 0805 King's Cross to Hornsey Depot ECS
5P51 1735 Hornsey Depot to King's Cross ECS
1P52 1805 King's Cross to Peterborough
5P52 1925 Peterborough to Peterborough Nene Carriage Sidings ECS
700/0
5C00 0432 Hornsey Depot to King's Cross ECS
1C00 0503 King's Cross to Cambridge
2C09 0627 Cambridge to King's Cross
1T12 0812 King's Cross to Ely
1T19 0947 Ely to King's Cross
2C20 1129 King's Cross to Cambridge
2C37 1327 Cambridge to King's Cross
1T40 1512 King's Cross to Ely
1T47 1642 Ely to King's Cross
2C48 1829 King's Cross to Cambridge
2C65 2027 Cambridge to King's Cross
1T68 2212 King's Cross to Ely
5T68 2334 Ely to Cambridge Sidings North ECS
700/0
5T86 1512 Cambridge Sidings North to Cambridge ECS
2T86 1529 Cambridge to Ely
5T92 1557 Ely to Cambridge ECS
2T92 1621 Cambridge to Kings Lynn
1G51 1716 Kings Lynn to Cambridge
5T59 1822 Cambridge to Ely ECS
1T59 1945 Ely to King's Cross
2C60 2129 King's Cross to Cambridge
2C77 2335 Cambridge to King's Cross
5Y90 0125 King's Cross to Hornsey Depot ECS
700/0
5Y03 0525 Hornsey Depot to Finsbury Park ECS
2Y03 0530 Finsbury Park to King's Cross
2C00 0621 King's Cross to Cambridge
2C17 0827 Cambridge to King's Cross
1T20 1012 King's Cross to Ely
1T27 1154 Ely to King's Cross
2C28 1329 King's Cross to Cambridge
2C45 1527 Cambridge to King's Cross
1T48 1712 King's Cross to Ely
1T55 1853 Ely to King's Cross
2C56 2029 King's Cross to Cambridge
2C73 2227 Cambridge to King's Cross
2R72 0019 King's Cross to Royston
5C73 0130 Royston to Cambridge Sidings North ECS
700/0
5C05 0517 Cambridge Sidings North to Cambridge ECS
2C05 0527 Cambridge to King's Cross
1T08 0712 King's Cross to Ely
1T15 0845 Ely to King's Cross
2R16 1029 King's Cross to Letchworth Garden City
5R16 1135 Letchworth Garden City to Letchworth Carriage Sidings ECS
5R33 1230 Letchworth Carriage Sidings to Letchworth Garden City ECS
2R33 1300 Letchworth Garden City to King's Cross
1T36 1412 King's Cross to Ely
1T43 1543 Ely to King's Cross
2C44 1729 King's Cross to Cambridge
2C61 1927 Cambridge to King's Cross
1T64 2112 King's Cross to Ely
1T71 2246 Ely to King's Cross
5E42 0028 King's Cross to Hornsey Depot ECS
The two 2Yxx services would normally be to/from Welwyn stabling overnight at Welwyn carriage sidings (engineering work this week). As can be seen, the 700/0 diagrams cycle round Cambridge, Letchworth and Welwyn carriage sidings, which presumably allows units to be rotated as required with units which are stabled. Normal GN 700/0 diagrams is something like 11, so there will be a considerable number of units stabled each day.
As can be seen, there's plenty of 700/0 activity to Ely, however only one return trip to Kings Lynn. Plenty of 387 activity on the 2Cxx and 2Rxx services, normally heavily 700/0 dominated apart from Sundays.
All Peterborough-Horsham and Cambridge-Brighton services are 700/1 as far as I can see, though there is a 700/0 out as I write this on a Peterborough-Horsham diagram.
One other alteration, 1C76 0032 King’s Cross to Cambridge changes from 2x387 to 700/1. Without checking I’d expect there’s an extra Cambridge to Hornsey Depot ECS somewhere to balance this.
This is all rather different to what was originally planned, as a result of Covid.