yoyo42 wrote:

What's the difference between a built-under and built-in oven? If I swap
an exsiting 600mm wide drawer unit in place of the oven then I could
then use that space for a full height unit and mount the oven in that.

Mostly, they can be swapped over. with a few adjustments. Built under
are taller, and sometimes have feet, so either the feet have to come
off (never tried it), or, you'll need to put a trim panel over the
feet depth.
Built-in are the typical slide in ovens, slightly shorter
in height than built under, around 70mm shorter. The built in are made
to slide into a 600 wide kitchen unit, which has internal width of
around 560mm. Most built-unders slide into the 600mm gap, between
adjacent units, they come with metal brackets that attach to the
adjacent cabinet sides.

However that brings up two more questions:
- that would mean there was a vertical wall of vinyl-wrapped MDF right
next to the hob. Would that need a splashback or something similar to
protect it from the heat?

Possibly/probably. Tiles are an easy, cheap fix for that. Custom
stainless splash backs can be bought, standard ones will be no good, as
typically, at least one edge has screw holes, which are hidden under
tiles, though if you can find one with square edge all around, then
that'll fit when you get the angle grinder on it - beware your cabinets
may be deeper than 600mm that splashback come in.

- I've only really seen contiboard stuff for sale, can nicer rounded
corner gloss white vinyl wrapped MDF be had for DIY or am I going to
have to buy the official kitchen units? I'll need to get a new door from
them anyway to finish off the full height unit...

Magnet trade sell to the public. B+Q et al have a range in stock, but
you'd be best finding where yours came from and buy the same.

--
Alan
To reply by mail, change '+' to 'plus'