Postcode Checker for UK Checkouts

Hello,

I’m in the UK and have recently moved my website to Shopify. Everything is great apart from the entering of addresses during the checkout process. Why doesn’t Shopify use a PostCode dropdown system for UK addresses? The current process doesn’t easily find an address, let alone fill in the full postcode.
The suggestion that we have to contact a customer to confirm an address only highlights an inadequacy.
Can a UK checkout not be introduced as a matter of urgency? It would certainly speed up and improve the process making for better conversion.
I believe this would be taken up by all the UK stores if offered.