Steve, yes the only thing that will lift the axle is larger tyres.
Springs are a suspension lift, they will lift the chassis and body which obviously provides more clearance under the body and improves approach/depart/breakover angles but unless you fit larger bump stops doesn't really allow you to fit bigger tyres as they can still come up to hit the bodywork.
A body lift lifts the body away from the chassis this means you don't actually gain much clearance underneath but approach/depart angles tend to improve fractionally. The advantage of the chassis lift is you can fit bigger tyres and still retain full articulation of the suspension. (I did my body lift to help lift my fuel tank which is different to everyone else)
Really I think a bit of both is the best solution but obviously costs more. Body lift is pretty cheap to do but more work involved so if you're paying someone to do it it will be expensive (LA Supertrux want about £1K inc vat). Lift springs aren't expensive either and they are easy to do. I changed the rears on mine in about 30 minutes and the winding the front up to match didn't take much longer.
TIP: if changing rear springs drop the shocks off their bottom mounts, this will allow the axle to drop far enough that you won't need spring compressors.