I couldn't get Joseph's solution to work above, as the second input field would still fill in the first input field, so this is based on his answer with some amendments.
I have two address form on the same page, and they display dynamically depending on the customer's previous selection, so I started by creating a unique id, then add the usual fields.
<div id="<?php if( isset( $postcode_context ) && $postcode_context == "collection") { echo "collections-autocomplete-fields";} else {echo "autocomplete-fields";}?>" class="new-address-fields">
<div class="fields">
<div class="row form-group">
<div class="col-xs-12 col-sm-6">
<label for="Address1">Building Number/Name *</label>
<input type="text" class="form-control field" name="Address1" id="street_number">
</div>
<div class="col-xs-12 col-sm-6">
<label for="Address2">Address line 1 *</label>
<input type="text" class="form-control field" name="Address2" id="route">
</div>
</div>
<div class="row form-group">
<div class="col-xs-12 col-sm-6">
<label for="Address2">Address line 2</label>
<input type="text" class="form-control field" name="Address2" id="route_two">
</div>
<div class="col-xs-12 col-sm-6">
<label for="Town">Town *</label>
<input type="text" class="form-control field" name="Town" id="locality">
</div>
</div>
<div class="row form-group">
<div class="col-xs-12 col-sm-6">
<label for="County">County</label>
<input type="text" class="form-control field" name="County" id="administrative_area_level_1">
</div>
<div class="col-xs-12 col-sm-6 wideField">
<label for="Postcode">Postcode *</label>
<input type="text" class="form-control field" name="Postcode" id="postal_code">
</div>
</div>
<div class="row form-group">
<div class="col-xs-12 col-sm-6 wideField">
<label for="Country">Country *</label>
<input type="text" class="form-control field" name="Postcode" id="country">
</div>
</div>
</div>
With jQuery as follows:
googlePlaces: function ($context) {
var placeSearch, autocomplete;
var componentForm = {
street_number: 'short_name',
route: 'long_name',
locality: 'long_name',
administrative_area_level_1: 'long_name',
country: 'long_name',
postal_code: 'short_name'
};
var componentForm2 = {
street_number: 'short_name',
route: 'long_name',
locality: 'long_name',
administrative_area_level_1: 'long_name',
country: 'long_name',
postal_code: 'short_name'
};
function initAutocomplete() {
// Create the autocomplete object, restricting the search to geographical
// location types.
autocomplete = new google.maps.places.Autocomplete(
/** @type {!HTMLInputElement} */
(document.getElementById('autocomplete')), {
types: ['geocode'],
componentRestrictions: {
country: ['UK']
}
});
autocomplete2 = new google.maps.places.Autocomplete(
/** @type {!HTMLInputElement} */
(document.getElementById('collections-autocomplete')), {
types: ['geocode'],
componentRestrictions: {
country: ['UK']
}
});
// When the user selects an address from the dropdown, populate the address
// fields in the form.
autocomplete.addListener('place_changed', fillInAddress);
autocomplete2.addListener('place_changed', fillInAddress2);
}
function fillInAddress() {
// Get the place details from the autocomplete object.
var place = autocomplete.getPlace();
for (var component in componentForm) {
document.getElementById(component).value = '';
document.getElementById(component).disabled = false;
}
// Get each component of the address from the place details
// and fill the corresponding field on the form.
for (var i = 0; i < place.address_components.length; i++) {
var addressType = place.address_components[i].types[0];
if (componentForm[addressType]) {
var val = place.address_components[i][componentForm[addressType]];
document.getElementById(addressType).value = val;
}
}
}
function fillInAddress2() {
// Get the place details from the autocomplete object.
var place = autocomplete2.getPlace();
for (var component in componentForm2) {
document.getElementById(component).value = '';
document.getElementById(component).disabled = false;
}
// Get each component of the address from the place details
// and fill the corresponding field on the form.
for (var i = 0; i < place.address_components.length; i++) {
var addressType = place.address_components[i].types[0];
if (componentForm2[addressType]) {
var val = place.address_components[i][componentForm2[addressType]];
$('#collections-autocomplete-fields #' + addressType).val(val);
}
}
}
// Bias the autocomplete object to the user's geographical location,
// as supplied by the browser's 'navigator.geolocation' object.
function geolocate() {
if (navigator.geolocation) {
navigator.geolocation.getCurrentPosition(function (position) {
var geolocation = {
lat: position.coords.latitude,
lng: position.coords.longitude
};
var circle = new google.maps.Circle({
center: geolocation,
radius: position.coords.accuracy
});
autocomplete.setBounds(circle.getBounds());
});
}
}
google.maps.event.addDomListener(window, 'load', initAutocomplete);
}
First time answering a question in full on here, so hopefully I have met the criteria. Thanks to Joseph, who this answer is based on.