Driving alternatives
I have tried driving from Malaga to Almeria and wouldn't recommend it - The journey seems to last forever, and the time is not that predictable, so you end up in the airport for ages on the way home.
Murcia to Almeria is much more realistic. I think it takes exactly 2 hours if you use the new toll motorway (€13 each way). Alicante is another 60km or so from Murcia, so add another 0.75 hours.
Put it this way, if the options are local UK airport to Murcia or STN/LGW to Almeria, I would chose the former, and do the 2 hour drive in Spain rather than on the M25. Of course, its even less if your final destination is Vera or Mojacar.
Its also worth bearing in mind that it takes half the time to clear the smaller airports of Almeria/Murcia than the larger ones, and the same is true in the UK, with BHX/EMA being twice as quick as LGW/STN.