Sadly I had further issues with my export last night. As previously mentioned, I tried setting multiple short export windows with reducing SoC. The first one to run having met the required initial SoC was at 18:00. This reached the target SoC of 55% half an hour later, before the scheduled end - and the batteries got paused!
Eco was off, switching it back on had no effect, and I tried a quick setting export again and that did nothing, although a quick setting charge did start the grid charging the batteries. Stopping the quick setting again put the batteries back into being paused. This time a soft resetting via the Giv portal did work (previously had to switch off/on).
I was leaving a ten minute gap between schedules as advised by @MrMessy in case there was a high temperature issue with the inverter (Incidentally, I noticed that WW was switching ECO off about 5 minutes before the start of the schedules, which wouldn't normally be much of an issue but means multiple 5 minute spells with paused batteries, which when you are cooking etc in the evening is wasting grid power - does there have to be this gap?)
The next two schedules worked, reaching the end before any SoC was reached but the third one, between 21:00 and 21:50, stopped and paused the batteries just after 21:35 having reached the SoC of 34%.
This time ECO HAD been switched on! As there was only about ten minutes to run before the (modified by WW) end of the schedule at 21:48 I left it, the batteries remained paused but at around 21:48 the batteries commenced supplying power again! (I wondered if that could be a clue, that the actual schedules have to come to an end, but then again others would surely have experienced this issue?). The last schedule ran okay, as it reached the end before the set SoC was reached. The IO schedule kicked in at 23:00 and commenced charging the batteries at the same time as Octopus started charging my EV, so at least that worked! I am at a loss to know what to do now!
Incidentally, I noticed the other day a post below from @iananguige (titled 'GivEnergy Settings'), which mentions the same issue of batteries paused on export, although on flux, but there have been no replies to it?