Best I'm seeing ATM would be an
HP 6012A (0 - 60V & 0 - 50A). It's ~$500 shipped to Spain (input voltage just needs to be rewired internally for 220 or 240V operation).
Manual.
You can also run a couple in series to meet your specs to come close to your budget (i.e. 2x Sorensen DCS 20 50, which is 0 - 20V & 0 - 50A per unit).
Off the top of my head, Sorensen, Xantrex, TDK/Lambda, and HP/Agilent/Keysight would be brands to look for (~ 0 - 20V & 0 - 50A is common enough). 40V models will likely end up costing you more unless you find a really good deal (i.e. DCS 40 25).
Another would be a the Lambda TCR 20S50 (
example; not sure if there's internal input switching for 230V or not, so need to check this out). The Sorensen DCS series has a 115/230V input so all you'd need is the correct plug.
Sorensen DCS Operations Manual (covers 24 models).
For disclosure, all of these ^ are SMPS models. Even if you manage to find a linear unit with that much output, I'd hate to see the price tag. Particularly in regard to shipping (locally would really be the only way you could manage this IMHO).
Hope this helps, and good luck.