thanks for the replies. it's a bit of a pain if you don't have a spare battery, you'd think the fob itself would be able to disarm the alarm. The alarm itself is always really quiet, even when the battery is fully charged, I'll have to take it back to the main dealer to get it looked at once lockdown is eased.
We have an 8 year old Aygo which was my main car until I bought the 86 and that can be left for weeks and still start first time on the original battery (may be tempting fate there), as does my wife's 4 year old Civic, seems like Toyota are cost saving by using the cheapest battery supplier they can, I won't be replacing mine with another Panasonic one.