As QB online does not support assemblies or manufacturing, we can not use it and will be cancelling our subscription. Sadly I cant find a number to call / e mail to call

Hello Useraccounts25, 

Welcome to the Community page, 

Thanks for this feedback, we will pass it on to our develops, and it maybe something that comes in the future, sorry you have to leave us as we don't currently support it. The number for the cancellations team is 0808 234 5337, then select options 1>options 3>options 2 and they will cancel your account for you there, it is open (Monday -Friday  9am-5pm and it is free from UK mobile and landlines).  

@useraccounts25 

You need an additional app to have the assembly feature and integrate it with your QBO.