Nothing like that out there for MGs unfortunately. Another MG forum tried to get it going but the logistics of it were a nightmare and there was a general lack of interest I believe due to how long the run would last.
It's a pain that you've joined us when you did as meets, runs & events are so dead in the winter. The next one which a load of us will be attending (& you're welcome to convoy up with us) is the Artic Circle Run - a must have for the insane MG enthusiast! Details of the next one are here:
http://www.mgfregister.org/forum/viewtopic.php?f=2&p=32543
...and pics from last years run here:
http://rides.webshots.com/album/570082054WbUKfO
Basically it's a load of F/TF owners driving round the M25 late at night all joining from different service stations along the M25 and all with the hoods down!!! So it's bloody freezing but bloody fun! And all for a good cause!