I would like to book a flight from London to Glasgow, including car hire departing in May, largely because I have a voucher that I need to use up, as it expires soon. My understanding is that leisure travel between England and Scotland will be allowed on the dates I am wanting to travel. If I search for flights only I can find suitable flights. If I search for flights and car hire I get a pop up

"Travel restrictions during national lockdown. It is illegal for residents of the UK to travel internationally on holiday during national lockdown. As a result we are unable to provide availability for your search dates".

This may be true but this is not an international flights, it's a domestic flight, so that statement is irrelevant as it is legal to travel domestically and holiday accommodation is already open. However the only option is "Back". When this banner appears I can see underneath suitable priced hire cars. Now I've tried being naughty and removing the pop up with the "Developer Tools" in my browser. If I do that it looks like I can go ahead and make the booking as I was able to select the car I wanted and click through as far as the payment screen.

However I'm concerned this may lead to questions about how I was able to make the booking given the website is trying to make it impossible. Am I likely to hit problems here?

I tried the app but I cannot seem to do a flights+car hire booking.

Any suggestions?