The stuff you are likely to see at Southampton central are 444's on the Weymouth to Waterloos which are usually 10 cars 450's on most other SWR mainline services including Portsmouths, the Romsey to Salisbury and rtn services are normaly 158's and I believe there is 2 diagrams for those services lastly for SWR there is one mainline service which is
2B91 1638 Winchester to Totton
and this is a booked 159.
XC services are all voyagers
SN services are normaly 3rd rail only 377's and one service a day goes via Parkway and Eastleigh
GWR services PMH-CDF are diagrammed 3 car 158s but 3 car 150 and 2 car 158s are sometimes used
Freight through central is mostly Freightliner 66s on the intermodals and 70s occasionally as well ,DB 66s on some intermodals aswell as infrastructure workings I believe there is only one GBRF working which is this one
4Y19 1230 Mountfield Sidings (Gbrf) to Southampton W Docks (Gbrf)
and will be hauled by a 66.
Eastleigh is the same pretty much however they only get one SN service a day and no GWR ones but they have SWR Waterloo-PMH services which are 8 and 12 car 450s and also occasionally a 59 on the Fareham stone trains. Eastleigh also has the SP next to the station which has 66s and colas 70s in it and the works are nearby which can have pretty much any thing in it.
If you get the chance there is also Southampton Maritime which has 2 resident class 08s which are 530 and 585 at the moment and Freightliner 66s and class 70s
and I think that is pretty much it