So this isn't really anything to do with Gardiners ? - more the courier firm they use.
And to get "free" next day delivery you have to spend in excess of £50, its a service I have come to expect from quality online companies.
There is an online warehouse for guitars and amps at the top of my street. They use Fedex couriers. They have at least two collections from 2 vans a day, you can almost set your watch by them.
Many online stores guarantee a next day delivery / same day dispatch if ordered and paid for by 2 pm, so it comes as no surprise to me really. You are getting what you have paid for.