BM2000 - no hot water following draining

Any help would be appreciated on this one, as my wife and I are at our wits end.

The system is a BoilerMate2000 in the airing cupboard with a Micron 40FF boiler in the utility downstairs.

We had a small leak in one of the rads downstairs and also wanted to fit a new radiator in the master bed ensuite, so we thought the opportunity was best to do both at the same time. The radiator in the ensuite was removed and replaced with a new one following a drain of the system by a plumber (hose was connected to the tap just above the boiler in the utility and drained outside).

Once everything was checked, we turned the system (both boiler and BM2000) back on to find we had no central heating and no hot water. The BM2000 powered up as normal, but I noticed the Store_T1 temp was showing as 20-odd degrees and not changing, and I hadn't heard the thermal store refill with water. The first pump (from boiler) seemed to be giving off a smell as though burning after a while, so I immediately switched off the BM2000 as I assumed there was no water in there! Called out British Gas (as we have HomeCare service with them) and the chap discovered that there was an airlock in the cistern in the loft and after a quick blow water started running back into the tank (although he did note is was a slow refill which took about 2 1/1 hours). He replaced the first pump and we fired up the BM2000 once the level rose about the pump level and after a few hours the temperature of the now water in the store climbed and central heating returned.

HOWEVER - we cannot get hot water working. When a tap is turned on, the DHW light on the ACB comes on after about 15 seconds, and there is the faintest hint of stone cold to luke warm water coming out the tap for about 5 seconds, then stone cold again. The DHW pump (farthest right) appears to spin (tested by taking off the cap and gently putting a screwdriver into the hole) but then stops after a minute or so.

Readings from the ACB are:

Store_T1 69
Store_T2 (PHE return) 59
DHW_T3 33

One thing I have noticed is when I run a hot tap, after about 10 seconds we used to hear the boiler in the utility fire up and the burner come on, but this no longer happens.

Any advice would be useful. I have tried to glean as much info from other posts and Mike's great advice, but I'd like to know what I should aim for before swapping out the ACB or the PHE return sensor.

Thanks in advance - Jon.

Sorry - a reply to my own post, but it's an update and hopefully(!) resolution.

It turns out that the BM2000 was still filling throughout the night and day (overall it has taken 2 1/2 days!) and so the upper portion of the store was not full enough to feed water via the PHE. I noticed the T3 reading as '55', ran a tap and it was warm/hot (plus now the PHE, surrounding feed pipes and pipe that is labelled 'Hot Water to taps' at the bottom of the BM below the pumps is toasty).

Glad it seems all resolved, but I'm a bit worried if we ever have to drain the system again. Anyone else come across this slow fill/airlock problem before, and more importantly know how to make the store fill up faster or manually introduce water into it?

Jon