Local pickup at single location when stock ordered from multi warehouse

[gayled]

We have multi warehouses that feed our single physical shop. 

We want customers to be able to order any item on our website that is available either in store or from one of our warehouses, and then collect them in store. 

- Either just allow them to collect within 3-5 days for the whole order if any item is being purchase from the warehouse

- Split the order so items currently in store can be collected within 2 hours and anything from the warehouse is available for collection within 3-5days.

All stock locations have local pick up on them at the moment, but we have an error occurring on checkout if someone selects local pick up when they are ordering a mix of items in store and from the warehouse.