Hello Colin,
Congratulations on your caravan, but I do have ask you to check your driving licence. My concern lies with the fact the GLE is a big car, and that means it will also have a very big Gross Vehicle Weight (GVW) or Maximum Authorised Mass (MAM), and when the caravans MTPLM is added into the equation its almost certain the combined MAM will exceed 3500kg in which case you must have entitlement Be or B+E on your licence.
A quick google using the search term "Merc GLE weights" tells me the GVW is 2950kg, that would leave 550kg for the MTPLM of the caravan.
If you passed your basic driving test on or after 1 Jan 1997 you will only have received cat B for cars under 3500kg MAM. If so you will have toi undertake the+E extension test
If you passed before 1:1:97, then you will have automatically been awarded entitlement "Be" so you'd be ok.