hey Rob.
what you are thinking of is called "tdt" (televisión digital terrestre) here, i have never heard of a dvb

but maybe that is what they call it in english.
what you want to look forr is a "receptor tdt" or "sintonizador tdt" and yes, the basic ones are very inexpensive and sold just about everywhere they sell tvs, dvds, etc...
have a look at
www.redcoon.es/index.php/cmd/shop/a/ProductList/cid/25002/Receptor_TDT/. there is one for 49 euros but i think they can be even cheaper at places like carrefour and alcampo (supermarkets).
a
SEARCH
on "tdt" will bring up a few good threads.
a lot of channels went digital in feb. this year. i waited and bought a tdt receiver last month and it is NOT what is is cracked up to be.
DO NOT buy one if you want v.o. stuff since the only channels that are v.o. are the same ones that already offer v.o.
there are currently about22 channels total in madrid (not sure of the exact number).
my advice is ONLY get one if you want to improve the image quality of your signal since the digital is quite a lot better than the normal analogical signal.
my picture improved a LOT with the receiver but the channels are not impressive at all (mostly crappy spanish tv).
also, they have a loooong way to go to improve the digital service. the audio skips often and sometimes there is no signal available so i end up turning off the tdt receiver and just watching tv via the normal signal.
and i have a pretty quality receiver as well so that can't be the problem. trust me, they need to improve a lot before it is considered a good system.
saludos,
jer...