Hey, I did this course in 2014/15 (and also had the option to transfer uni's after it, but declined my offer as i chose to take a year out, earn some money, and return to Portsmouth this september).
Maths start at the very basics, and if the lecturer is still the same guy, he is absolutely lovely, honestly the best lecturer you could possibly ask for (his name's Richard Treloar if you wanna search for him).
I came in with a BTEC and could literally remember no maths from school and I coped fine (mostly thanks to the support from richard).
I think it starts with basics GCSE stuff and ends with about A2 Level maths.
Make sure you complete every worksheet he gives you cos they help so much.
And not to keep going on about it, but honestly Richard is fantastic, he really tries his best with each student, I can't praise him enough.
Facilities are good, most buildings are fairly modern on the inside, the library has loads of computers and plenty of space (except for around exam time, but that's the same at every uni I suppose).
Most of your lectures will most likely be in the Portland lecture theatre as there are so many students on the course (around 200). However your maths will most likely be in Anglesea or Buckingham buildings since you're split in group A and group B (however you can go to both maths lectures/tutorials. I did this which most likely helped me understand the maths as I was getting twice the amount of contact with Richard haha)
Even though it's a city campus, everything is extremely close and you don't even realise it's a city as there's so many students everywhere!
Passing grades are about 50% for most BEng courses and I think 65/70% for MEng courses.
Most people I know managed to get onto the MEng as long as they put the time in (I quite easily managed to get 98% in the electrical module, 94% in maths, 81% in thermofluids and dynamics [the in-class computer test brought my grade down as it was hit and miss for each student], and 80% for materials [once again, the grade was brought down by the design aspect of this module as most people only got 50-70% for their designs]). Just make sure you go to every lecture as missing 1 or 2 in a week can easily put you behind everyone else.
I can personally vouch for this course and I highly recommend you do it as I honestly had the best time at Portsmouth and can't wait to return in September!
As long as you put at least a bit of effort in, you'll be fine. I still managed to go out drinking 1-2 times a week even around exam time!
If you feel you're struggling with any part of the course, the lecturers reply extremely fast by email and have a fairly open door policy.
Also there's plenty of maths / physics support through the maths cafe and physics support tutors.
Finally, I knew of many people transferring uni's after the foundation year (I knew of someone managing to get offers from Newcastle and Surrey). However, if you plan on doing this, make sure you apply before the 15 January deadline.
Also, Portsmouth may seem like a fairly mid-ranked uni, but the quality of teaching and support is top-notch, which is the reason why I've decided to return in September (plus, you'll be doing an engineering degree so your gonna get a job wherever you go! :P)
What I realised when I left for the year was that it's not about how high-ranked your uni is, it's about where you enjoy being and I personally loved every part of Portsmouth; everything's compact, it takes 5 mins to get to the beach, the lecturers will help you with any question no matter how silly, and watching people get blown across the street because of the strong winds will never get old :L.
Good luck!