Airlines will not provide hotel stays for change in schedules (not only in India pretty much anywhere, the only thing is they will try to accomodate you on a different date/routing). The way I see it is either accept the routing they give or the other option is request them for 100% refund and book through some other airline/routing.

The other option if you do not want to wait so much time in BOM as well as CMB airports with there current routing, you can request for a routing through MAA for example GOI - MAA on the 23rd through Paramount airway spend the night at MAA and then take MAA-CMB on 24th morning through Sri Lankan to connect to LHR.