I have returned back to St Denys since 2019 was my last visit.
It is situated on South Western Mainline which also serves West Coastway Line, and is one station stop from Southampton Central! Here we have huge variety of trains, mostly passing through and 4 trains stops per hour and few additional services which runs in peak hours. You will see trains that are featured, which are South Western Railway 450, 444, 158, Southern 377, Great Western Railway 158, 166, Cross Country 220, and lots of Freight Class 66 & 70. St Denys is incredible little station, and also very busy train traffic, and it has a charm to it. There are two part track section that splits, one which is South Western Mainline, The Midlands & The North. And the curve track serves West Coastway Line. And you have a cracking view of the track layouts that leads up to Southampton and the bridge in the center, and also Southampton Yard.
I thoroughly enjoyed my day here, and will definitely will come back again in near future.