Fluent Forms.
Native Address field, free core, wired automatically.
Fluent Forms includes an Address field in its free version, so the plugin detects it and attaches UK autocomplete with no configuration. It is multi-form safe, so several forms on one page each behave independently.
Three steps.
Install the Postio plugin and activate it.
Go to Settings → Postio, paste your API key and press Save key.
Add a Fluent Forms Address field to any form and start typing into line 1.
Details.
Line 1, line 2, town and postcode all populate from a single selection.
Using something else?
UK address lookup on the block and classic checkout, plus My Account addresses. No configuration.
Every Address field on every form, wired automatically.
Automatic on WPForms Pro. On WPForms Lite, two minutes with CSS classes.
Native Address field with sub-inputs, free, wired automatically.
CF7 has no address field, so you tag yours. Two minutes, once per form.
No address field in Ninja Forms, so you tag yours. Two minutes, once per form.
Elementor Pro only. Tag your fields with CSS classes and you are done.
Ready in under a minute.
Sign up, grab a key, paste it in. Your first hundred lookups are on us.