If the vinyl is well stuck down then yes, you can paint over it no problem, I was quite surprised when I for saw this done, but it stick well and ive never seen it flake.
Straight on with two coats of matt or silk....but you may be dissapointed with the result, joints that you cant see now may show up once painted.
Its fine if your looking for a quick fix.....if your looking long term, as Minul says, you really should strip the walls, making sure you give them a really good scrub too in order to remove any excess paste. Better still, line it then paint it.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local