Managed to get back to Grantham today, so I have now mapped the new sliproads for the A1 Northbound, and added a small section of the B1174 heading towards Allington (although I didn't get that far). I've added the new A1 Southbound section, although I've left the sliproads as they were as it's not yet clear whether these will be moved / realigned by the roadworks.