Popup on website to collect data

General information for the website: Luxury bathrooms
Description of requirements/features: Hi there!

We have had so many problems with someone we hired to do this job (friend of the family!) and he let us down, we desperately want to get a new feature added and hope we can find someone on here instead.

We have a custom website using html/php/css. We would like to add a Pop-Up to the website with the following:

- Pop-Up invites the customer to leave their name and telephone number
- The data is emailed to us, nothing is emailed to them
- The Pop-Up isn't invasive, can be X'd easily, or a button to 'never show again'
- The Pop-Up doesn't hit the user immediately on opening the website, maybe after 30-40 seconds instead
- Once the user has entered their details, it doesn't display to them again unless they clear their cookies
- We can somehow manage it - change the design, change the email address should we need to - my daughter designed the website so has some knowledge in this area but the actual pop-up exceeds her skills

We have very limited funds for this job and hope someone can help!
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