The connection application/offer/agreement would normally be confidential.
The Transmission Entry Capacity register doesn't show demand connections but does show generation projects being developed to connect to the transmission system. There's some at sites originally developed to supply the railway, such as Market Harborough and Patford Bridge. There are a couple of mentions of "Kegworth B 400 kV" substation, which I am pretty sure does not yet exist... They are looking to go live in 2033/34, so presumably NGET are advising them that they expect to have something for them to connect to by then (not much help, I know).
Haven't seen anything from National Grid on Rushcliffe planning portal, but am not checking and not expecting it before the comprehensive spending review. in May 2025.
It took NGET about a 9-12 months to obtain planning permission for Market Harborough, then there was a 2.5 year gap before work started on site, and a 2 year build phase. Assuming the 2.5 year hiatus was Grayling-related, then I'd guess a planning application in mid-2025 means 2028 or 2029 for energisation.
That's still online, see:
https://www.find-tender.service.gov.uk/Notice/029689-2023#amendment-1