Temple seems so new, but the shrine is 300+ years old. We finally managed to chat the priest up a bit. This was the Ezhai Vinayaka temple, land had been encroached by buildings behind, took them 7-8 years to remove the encroachments, and then to raise funds for the current temple. Kumbhabhishekam happened last September, presumably at Chaturthi.
The Brahmotsavam is at Chaturthi – Dhvajarohanam on Chaturthi, Avarohanam on Pournami.
Temple seems to have a bit of everyone – Ayyappan, Hayagriva, Venkateswara & Garudalvar etc. The Vishnu form was apparently a koshta murti that they did pratishtha for, so kept separately. Ayyappan Sabari malai devotees come here in preparation. One lady who was there comes to sing bhajans. They propitiate all the deities there on the appropriate days (Krittikai etc.). Veethi ula only during Brahmotsavam and Masi Maham. All the deities are small, a foot or so, including the Vinayaka who looks like the Manakkula deity, down to the metal ornamentation of his body and beaten brass cladding in his shrine. Smaller deities have more power, says the priest.
The priest mentioned the fact that the 8 year gap had impaired the flow of devotees – people with flower shops nearby have died, regular devotees go elsewhere now, and there’s a need to drum up interest with a YouTube channel or other social media posts. Used to be a temple for all the poor in the area (at the end of MG road), but has since become the Siddhi Vinayaka temple.