Boiler making loud noise

I had no hot water this morning although the CH was working fine. Nothing came out of the hot water tap in any rooms. In the afternoon i switched off the boiler from the mains and back on. After running the tap the hot water came back but 5 mins later the boiler was making a loud clunking/banging noise. I switched it off and then back on but it immediatly came back. Tried it 1 hr later and it seems to be running fine now but worried ot leave it on. Engineer cant come out till 2 days.
Could it be that there was some ice in the system and it had'nt melted or maybe something actually broken?. I have a Ideal Sprint Rapide 90nf combi boiler which is quite old but seems to run fine up to today.
The pressure gauge reads between 0 & 1 but not sure if thats what it always is.

As its working ok now I would suspect frozen pipes.Insulate as much pipework as you can and think about replacing boiler.These must be getting on for 20 yrs,and compared to a modern boiler are poor performers.Mind you,new ones won't last as long as that one has.
PS pressure should be about .75- 1bar when cold.

thx for the quick reply.
With regards to the pipework do you mean the pipes coming immediately out of the boiler? The boiler is housed in a cupboard in the kitchen and the pipes go down through it so i guess they are exposed to low temperatures compared to other parts of the house.
Would those pipes if frozen have caused the loud noise if maybe ice got into the system making that racket.
The boiler is around 19 yrs old been meaning to replace it.

Under the current conditions, don't turn the boiler off at all, but lower the roomstat for overnight.