Awning Width

Depends which sites, there is a fair variation in pitch width, if you mean the hardstanding.  Newer ones seem to be a bit wider.

That's a fair size and I suspect there will be pitches where it won't fit. Don't forget that total width of 5.25m will need to be from the peg to the far edge of a HS and not necessarily from edge to edge.

We are 4.8m plus guy lines, Aquaroll space and car, it was a very tight fit on our HS at Putts Corner, one wheel of the car was off the HS.

At Banchory, the HSs are much wider, but pitching to the peg left us with unused space on the awning side and a wheel on the grass.

On a CCC site at present, the HSs are 5m wide, so we fit, but Aquaroll and car are on the grass.

Our Knaus is also 2.5m wide and we have two main awnings - one a Kampa 390 Grande which is a full 3m deep and the other a Sunncamp 390 which is just under 2.5m deep. We've never used the Kampa on a Club H/S pitch and, to be honest, I think we would struggle on most to fit in. We tend to use that one in the summer when we would (out of preference) be on a grass pitch and more than likely on a CL or CS. Since we use the Sunncamp in winter and then would choose a H/S pitch, we haven't had a problem, so far, but our experience re Club sites is limited since we are not big fans of such sites because they tend to be more cramped. I know we are OK at the likes of Sandringham (for Christmas!) and Chatsworth but I can think of others were you struggle to fit in any half-decent sized awning, plus car, aquaroll etc.

We have a Valencia which is the same width ,and a Kampa 390 ,and as yet have never come across a pitch ,which was for a caravan with awning, that did not fit
So width you should have no problem 
Just a word of warning, the new Dometic 390 has been highly modified to fit both motor homes and caravans, it also has two different sizes beadings ,The height is adjustable by the use of zips, and held together with large Velcro Strips 
The twin size beading drags on the awning rail making pulling on harder, as one of the beadings drags on thee awning rail  
You have to be careful where you pull the awning from, as the Velcro separates
Tht quality is not as good as the old Kampa

We had terrible problems with leaks from the beading ,awning rail ,and one of the roof panel held  so much water it bowed  the air bladder pumped to 9psi   and the weight of  the water forced the waster though the weave of the roof fabric 
As it was new we rejected the awning and took it back for a full refund