When sintalling a new gas central heating system, is it normal to insulate all the pipes ?

you seem to post a lot of questions on here that dont need to be answered. Any good tradesman does what is required why ask is this noramal? you will get cheaper prices for any job, tradesman charge what is required other people charge what they can get away with. there are a lot of customers that think they are clever saving a pound, then spend a day asking is it right? give the tradesman a chance if they are qualified and not the cheapest it usauly works out cheaper! Does your boss go on here everyday asking if you have done your job right? :-)

In short....yes. Common practice. Reduces heat loss on your pipework. Which in turn can make it more cost efficient to run.

No not all the pipes. If the primary flow and return are positioned subject to considerable heat loss then it is advisable. The pipework in the airing cupboard around the hot water cylinder should all be lagged as far as is visible.

I would Insulate the pipes in any unheated area I.e. Garage, loft, boiler house and if pipes are underneath the floor on the ground floor. Also regs are one meter on all hot pipes from and to a cylinder but as above, as far as you can see. Often people don't want to pay for the lagging but this is definatetly good practice