I LOVE Desperado's Tequila beer, but it's not exactly cheap if you drink a lot of it !
I've found a few alternatives for your consideration - if you know of any others, post them up please !!!
Desperado's - £1.50 per bottle (£1 per bottle if bought in a crate of 24 from Costco) - 5.9% ABV
Amigo's - £1 per bottle (4 for £4 from Morrisons) - 6% ABV
Salito's - 79p per bottle (B&M - going to stock up tomorrow - tastes very very similar to the above, but half the price) - 5.5% ABV