The Tuscan Expert ;-)
Staff member
The website for the church is offline for some reason, so I contacted them through Facebook and got a reply:

For the S. Andrea church (main one in Montespertoli)
Monday - Thursday - Friday - Saturday
7.30am and 6pm
9.30am and 6pm
Sundays and holidays
8.30am - 11am - 6pm

Other churches in Montespertoli:
S. Pietro in Mercato - Sundays 11am
S. Bartolomeo a Tresanti - Sundays 8.30am
Cuore immacolato di Maria at Ortimino - Sundays at 10am
Casa di Riposo S. Maria della Misericordia - weekdays 9.30am, Sundays 10am

Hope this is useful!