Malky Mackay will give the 21 year old a couple of weeks off now with the rest of the squad due in on Wednesday.
"The fact he's had the experience being away with England at international level and being involved in an international football tournament at such a high level is great for him and it can't be bad for Watford either," mackay told the official Watford website.
"We'll give him a little break before he comes back so he will get a proper rest before he is needed to play for us in the late pre-season," added Mackay.
"Scott will meet with our conditioning coach, but it's great that he's been ticking over his fitness with the England training."