There is specific jack, along with brackets for Bailey's. DONT ever jack on just tge chassis rail, it will bend and break the galvanising. If you don't have/don't want the purpose built brackets and jack then I would advise you get a low profile trolley jack so you can get it under the axle as close to the wheel as possible. A bottle jack is fine until you get a flat tyre, at which point it's too tall to fit underneath any other than the chassis rail (see above!)
As for wheel nut size, check tgey are all a standard hexagonal nut, my Bailey (2019) has WSL nuts that need a specific tool and cannot be undone with a standard socket. Earlier ones had a single WSL as an anti theft measure.