Complex sentence: When Lord's is hosting a Test match, only members of the MCC are permitted in the pavilion; however, for all other matches, members of Middlesex and their opponents are also permitted in the pavilion with the option to bring in two guests.
Split into simpler sentences: When Lord's is hosting a Test match, only members of the MCC are permitted in the pavilion. However, for all other matches, members of Middlesex and their opponents are also permitted in the pavilion with the option to bring in two guests.