Opinions from someone who does a LOT of flash/strobist portraiture on location.
1) Don't spend it all at once on your lights. You'll need grip gear and accessories too - triggers, light modifiers, light stands and boom, backdrop stands, backdrops and/or paper, clamps, sandbags, etc etc.
2) Learn to do manual flash power. In a studio setting, the automatic modes will lead to frustration, because the system will adjust the flash power based on what's in the frame - even minor changes in pose or camera position will affect the calculated exposure, so when you shoot a whole set, your exposures will be all over the place. Once you've dialed in your exposure to properly expose the skin, you don't want the camera to adjust the exposure when the model changes from a white shirt to a black shirt.
2a) Automatic flash settings (ETTL) are great for run-n-gun, on-camera flash, where you have one chance to get the shot and "pretty close" is good enough.
Having said that. With that budget, you can get quite a bit. You might even get a set of strobes and a set of Speedlights.
Speedlights pros/cons:
+ Generally less expensive than studio strobes
+ Lightweight, easy to carry and transport
+ Fast to set up
+ No cords to plug in
- NO MODELING LIGHT (this is a big one for portraiture, where precise positioning of light and shadow can make or break a portrait)
- Less powerful than studio strobes (generally won't matter unless you're outdoors)
- less variety in modifiers
Studio strobes pros/cons:
+ Modeling light
+ Lots of power, even the entry level ones are more powerful than Speedlights
+ Lots of variety in modifiers
- More expensive
- Heavier, bulkier, harder to transport and store
- Needs a power outlet (unless you go to the high-end ones like Profoto) or battery pack
I have a set of both. For my Speedlights, I have one 430EXII and two Yongnuo 560EXII's. For my studio strobes, I have two entry-level Elinchrom D-Lite 2its.
I don't know if I would recommend the Yongnuos right now; I've gotten a lot of good use out of mine but they're getting on to four or five years old, and there's better stuff out there now. When these finally wear out, I might change to Godox/Neewer speedlights.
Elinchrom is a Swiss company and has a lot of support in Europe. Their new modifiers are often available in the UK before they're available in the US. Some brands of strobes that are popular in the US might be less available or less supported in the UK, I've heard anecdotes but have no specifics about them.
If you look in my gallery, about half were shot with my cheap and easily portable Speedlight kit. The smoke shots were a combination of one studio strobe and two Speedlights.