I have three separate lighting circuits, one for each floor of the house, each connected to a 6A type B MCB in the consumer unit.  We have some ceiling mounted light fittings consisting of 3 and 5 lamps each.  When a bulb goes in one of these fitings, the whole circuit trips out.

Could I get round the problem by replacing the MCBs with Type C (I've read another topic somewhere on here that states the disconnection time is slightly greater for Type C and can therefore combat this poblem).  Someone else also suggested that I try repacing with 10A MCBs - is this a good idea?

I would suggest trying 6A Type C MCB's, you can't just upgrade to 10A withought having an inspection to ensure all the cable will take the load.

You should really have the circuit tested to ensure a Type C will meet disconectiont times, however if it meets type be which it should do, then it's likely that Type C will meet, They are quite close in relation to maximum impedance.

Yea, not much need for a C10 on a domestic lighting circuit tho, unless your circuit is using close or near to 10A and you want that surge discrimination.

No problem andy

I think you will find it cure's it, altho you may have to wait awhile till a bulb blows  

Thanks to everyone who replied.  

I actually got some Type C MCBs (from ToolStation - miles cheaper and more stuff than Screwfix by the way).  Waited a good couple of weeks then lo and behold, like buses, three lamps have gone in the last week!  Circuit didn't trip out!!   Woohoo!!

Only cost me about 12 quid for the new MCBs so am very chuffed (so is the missus as she now doesn't suffer a blackout when I turn the lights on during her morning shower!).

Thanks again.