Hi I have had the E3 and now have the vibe.
I have found the vibe seats more comfortable for the dc. My ds always looked cramped in the front seat of the E3.
I prefer the break on the handlebar especially when dd tries to run away (although when I first got it I did push it accidentally a few times)
The seat straps are easier to use (although imo not perfect).
The sun shade is excellent can be pushed up and down the buggy and cover the front part of the buggy. This helps if you have a child on the top seat the hood fits over them, on the E3 my ds head used to hit the hood. I also had a real problem shading the front child in the E3 with the vibe the hood just flips to where you put it.
I haven't found it heavy at all and I can push it with one hand with 2 dc in buggy and a baby in the sling. It weighs less than the e3.
The fold isn't great when you put it in the car. The E3/Sport fold is much more compact.
The vibe cocoon is wider and the sides don't collapse in like the e3 cocoon. Is it worth 20 quid more? Probably not. Try and pick one up second hand maybe. I will try and check to see if E3 cocoon fits in vibe but I shouldn't see why not.
The footrest on the vibe is hard, on the E3 it was fabric and ds used to push down and try to stop the wheel.
I wouldn't personally buy the p & t sleeping bags for the buggy as I don't think the fit is great.
I haven't found that the vibe seats are close together as someone else mentioned maybe the front seat just needed to be strapped up higher.
Basket access is probably better on E3/Sport as you can undo the poppers you can't do this on the Vibe.
Have a good time buggy shopping.