For me the EUB is either a different instrument (to hold and which kind of music is best suited to it) or a more portable (but not neccessarily lighter) instrument to replace a double bass in rehersals or in gigs with less space.
My big band leader usually insists to use a real double bass in the concert.
Since I have grown up with double bass, not bass guitar, with a good (and more expensive) instrument you get most of the feel of a real double bass, but not the sound. This might be OK for larger/louder ensembles where an amplified double bass does no longer sound like an acoustic one (and needs to sound different to get through the sound of the large ensemble), but for smaller groups specially if they all use acoustic instruments, it sounds different.
Bowing on a EUB is more difficult than on an acoustic instrument. This does not matter for a few longer notes, but if it gets rhytmical or faster, you might have problems on an EUB.
I don't think an acoustic double bass needs to be more expensive than an EUB. Cheap EUBs and cheap double basses are ... cheap. They may have or become problems. A few might be OK (maybe the Warwick Triumph Lite for an EUB). But for the same money you can get asian or romanian double basses. (OK, you need a pickup and maybe a wheel or better a Bass Buggie for easier transport too.)
It seems you are located in the UK. A lot of UK players are happy with cheap double basses from Gedo-Musik in Germany. I have played several of them in their showroom, they are OK for your budget. Have a look at the UK basschat.co.uk forum. They are from asia or romania. I talked to the owners and they told me that they only buy good manufactured instruments that won't fall apart after a few years. US or european hand made instruments of course won't fit your budget, a lot of the a bit cheaper ones are relabeled asian or east european instruments with a local setup.
I take my EUB to the rehearsal because around 5PM the busses, trams and trains are so full that I would have problems with my double bass. I also take it into my holidays (by car) because it doesn't take any useful space (I hang it onto the dog separation lattice above anything else). But even this EUB (CLevinger) is more expensive than your budget. My cheaper Stagg is hardly used at all (it s more like an instrument for experiments or for sporadic use). It is useable, but bowing is harder than with the Clevinger (wobbly body support) and I won't like to have this as the only instrument. (If you have an acoustic double bass it would be OK for the rehearsals of the big band.)
I would stay away from the NS EUBs, since they are rather upright electric bass guitars than double basses. For the feel and preparation for double bass get an instrument with an endpin, not a tripod-based one.
For a really cheap EUB read the Palatino and Stagg megathreads (completely!). The RDL rosewood fingerboard Stagg sounds much better than the cheaper ones, but still has the wobbly body support. For the cheap ones, check before you buy that there are no buzzing spots on the fingerboard using low action (G 4-5 mm, E 8-9 mm at the end of te fingerboard). And i mean spots that buzz more when you press the string down there than a few centimeters up and down. Do calculate a new set of strings (at least £120 for a decent set) too since the factory strings are often cheap.
And never buy an instrument before you haven't tried it. Better get a teacher now, rent a double bass for a few months and then you (best together with your teacher) can decide what is the best instrument for your budget.
