Can anyone recommend where we should look for long-term rental properties?
Well, Almeria Province is about 4 times the size of Tenerife, or about the combined size of the counties of Kent and Essex in terms of km²! So it's a big place.
It's also worth pointing out I think that mainland Spain, particularly Almeria, will have more extreme temperatures than Tenerife. Tenerife tends to have a better year round climate—it's cooler in Summer and warmer in Winter. Almeria on the other hand can get very hot in Summer, June, July, August can easily push mid 90s and higher, inland can be even hotter without the cooling coastal sea breezes. Winter tends to be colder, particularly when the sun goes down, out of the sun it can be quite chilly. So you might want to bear this in mind when looking at properties. You'll probably want to look for some form of a/c for those summer months and some form of heating for winter. Cooling and heating obviously have costs associated with them.
As to where to look, well all along the Almeria coast are nice locations, it's a very nice part of Spain in my opinion, but then I'm biased because I have a property there!
If you want to be reasonably close to a British expat community, without necessarily being in it, I'd suggest you start with Mojacar and radiate out your search from there. Mojacar has quite a thriving expat community, but there are plenty of very nice places further up the coast both North and South from Mojacar. Vera, Vera playa to the North and Carboneras to the South for example.
As a general guide, you'll find Villas inland and apartments on the coast, both have their own strengths and weaknesses, pluses and minuses. That's not to say you can't find Villas on the coast, you can but they're generally a lot more expensive than their inland counterparts and inland apartments tend to be cheaper than their coastal counterparts.
The advantages of Villas is their seclusion, privacy and quietness (if you're lucky). The downside is they may not necessarily be close to amenities, shops, bars and restaurants etc and if inland will be hotter than properties on the coast. It's vice versa for apartments, they may be closer to amenities, but will be generally noisier. What you go for is obviously down to whatever priorities you might have.
I'd suggest using some of the property websites and get a feel for what's available in what place for inland villas and coastal apartments. Use that knowledge for when you go there to look yourself, because there's no substitute for simply going to the place and getting a feel for whether you want to live there or not.