Right problem solved I thought I would double check the rose in another downstairs room and it only had one cable I thought strange as I thought all lights would be looped at rose so checked switch in room and as I opened it all the "looped" browns came out from the terminal, put them back and all working. Is it normal to have a mixture of rose and switch looping. I'd like to thank all those who responded I will visit again.
There is NO requirement to wire any lighting circuit in a specific way..
Providing that the circuit meets the essential safety requirements of BS7671 wiring reg's, (to protect people, property and livestock by disconnecting the supply fast enough to prevent danger).... you can connect the cables how ever you like!!!!!!
It is most often decided by a mix of:-
(a) building structure,
(b) easy of getting cables to where they need to go, {e.g access under floors/above ceilings.}
(c) shortest cable route between items that need to be connected,
(d) personal preferences/fetishes of the person installing the wiring...
(e) other options I am too lazy to consider and type!!!
A basic essential rule when working, (fault finding or extending), on any lighting circuit that you have no personal previous experience of is: "ASSUME NOTHING" until "YOU HAVE PROVED SOMETHING" about how the circuit is wired.
P.S.
That back-box & switch do appear to have an excessive amount of cables and wires pushed into individual screw terminals..
[Personally I would prefer, deeper backbox and a few miniature push-fit wago's to reduce the number of conductors into screw terminals]
Plus NO brown sleeve to indicate any "switched live" conductors....
UNLESS as previously mentioned... your wiring is switching the neutral!!!
Which as others have said is a "BIG-'NO'-'NO'"