I completed my 2357 NVQ with XS a couple of weeks ago, so would like to leave my thoughts.
Firstly, in my opinion the portfolio aspect of the NVQ is worthless, it is nothing more than a frustrating box ticking exercise designed to create revenue for the training sector and does nothing to prove competance. Of course that is a general criticism of the system/qualification rather than XS as a training provider...
Overall XS did a good job, and getting through the portfolio was in some ways easier than I expected but I did find it quite frustrating at times. It took me about 15 months start to finish, I had pretty much completed the portfolio in 12 months but decided to have a 3 month break before sitting the AM2.
Would I recommend them? Yes, provided you are OK with remote observations (zoom call) for site visits (see below). Overall, I'd consider them a reliable NVQ provider - other people I have talked to doing the NVQ with other training providers seem to have had a much worse experience...
The sites I was working on were very poor for mobile phone signal, so it was sometimes quite difficult to arrange suitable work for the observation in a part of the building with phone signal. This was something I hadn't considered when I signed up - bear in mind many commerical and industrial buildings are terrible for phone signal due to their construction (lots of concrete & steel).
One of the things that did irritate me was not really knowing how far through the NVQ you were. The OneFile web platform they use has a progress indicator, but it isn't updated very often so is pretty useless. XS could improve the experience a lot with a better explanation of the process they follow, either write a document or explain it better in the initial discussion with assessor.
[XS, if you are reading this and want more detailed feedback, PM me and I'd be happy to give feedback privately]