Goodwood

MGOC and Moss Europe both offer reconditioned engine services:

https://www.mgocspares.co.uk/parts/1_3_977_978_979/reconditioned-engines

https://www.moss-europe.co.uk/full-engines.html

The MGOC also has a workshop where they could install it. Not sure about Moss Europe.

You are not in the UK, so I am not sure if you want the engine shipped to you or if you want to travel to the UK with your car (if you can).