Should my boiler be doing this?

A couple of weeks ago I had my annual service with British Gas and he fixed a couple of faults, and left saying the boiler is working perfectly and efficiently.

However, it seems to be working different than it ever has done before. It's gravity fed hot water and we've not got the heating on in this weather, so it's just set to hot water only.

Previously, from cold, it would fire up for a few mins then switch off once at temperature (and you'd feel the flow pipe up to the cylinder get hot). A few minutes later it would happen again, fire up for a few mins, then go off. In short, firing for 4 mins, off for 3 mins, firing for 2-3 mins, off for 3 mins, firing for 2-3 mins, and so on repeatedly.

Since the service, it fires up the first time for a few mins as before then goes off for a few mins. Next time it fires up it only fires for between 1 and 10 seconds then goes off for 3 seconds, then fires again for seconds, off, repeating this several times, before there'll be a longer fire (30 seconds or so) then it will go off for a few mins before doing the same again. In short, firing for 4m, off for 3m, fires for 2 seconds, off for 3s, fires for 2s, off for 3s, fires for 10s, off for 3s, fires for 1s, off for 3s, fires for 30 secs, off for 3 mins and repeat.

As it makes a loud click each time it fires up, this new sequence of events is a lot more annoying as I can hear a loud click every few seconds every few minutes.

However - it is heating up the water perfectly, probably quicker than before, so without a fault as such it would be £99 excess for me to call BG back out to ask them if it's operating normally, especially as they've just done the service and told me it's operating well and efficient.

Does anyone know if this is "normal"? Why would it fire, sometimes literally only for 1 second before going out again then firing for another second just 3 seconds later.