Not sure if you'll get this in time but here goes.
The main thing they're going to want to see at the interview is that you're passionate about design and not going to be wasting a place that could go to someone else who really wants it.
Show your work, be confident and enthusiastic and try to use as much design terminology as you can ('typeface' rather than 'font' for example).
As for the assessment, I never did one but I suspect anything related to key skills (reading, writing, maths) is more to identify where you may need help rather than to 'test' you. This is the case I've found with KS subjects anyway.
I was expecting something big but it wasn't that hard. A took some sketches with me showed them my portfolio and than they asked me about the software, drawing and sketching skills etc but didn't asked me to do anything. It was basicly an introduction type interview. And finally I asked to do a basic level of (computer based) English and math test which in Math I got Level 1 (required) and in English Level 3 (very high). As Paul advised me that you should show them your passion about Art and design. Be confident about it. Thats All...
thank you!! i am applying for GD @ salford uni (MCR) manchester met & camberwell LDN (open day next thursday excited much just booked my train ticket ) .. not sure about any others yet, still investigating! in a bit of a rush gotta go but shall be back soon hehe :icon_biggrin: