If your hammer drill is an SDS you can get a SDS drill chuck for standard drill bits (no hammer action with the chuck but that's what SDS bits are for).
I found the Bosch PSB 18V Li-2 (Li-ion) a decent drill - driver. After 3 years it's still going strong (including putting large 150mm bolts in the walls, coring ceilings etc). The only downsides are - the aggressive brake can loosen the keyless chuck and it's form factor is bigger than a simple driver. It's not an impact driver - this means it can hammer but not provider the pulses of rotation torque that an impact driver has for long length screwing without pre drilling (but it's not a slouch in the torque department). The PSB doesn't have a safety clutch required for masonry coring.
However it has two speed with torque control (can set the limit which is great for screwing soft woods/MDF), it's drilling is good and the hammer action is decent too with variable speed control. The B&Q offer has two fast recharge batteries it's always available. Also you need that larger form factor if your drilling to get the right accuracy. Lastly it has LED lights that light up the drilling area. Lastly it can be used one handed - including selecting forward/backward easily..
B&Q for £98:
http://www.diy.com/departments/bosch-psb18li-18v-li-ion-cordless-combi-drill/258347_BQ.prd
I have it's bigger brother now
An 850W Bosch SDS drill in the 2Kg size. The Li-ion PSB is great for 80% of tasks - and it's the first drill I will pick up. Although have seen the SDS 3.2J hammering in action.. it does make the PSB seem a little less hammer and more 'purr'
However it's 'purr' has done me proud putting bolts in masonry.
It really depends on the overlap of your equipment and if you don't want to the hassle of pre-drilling large length screw holes where an impact driver would be better.
As a screw driver I'd look for:
* variable torque limit - this means you won't sink the head of the screw into soft wood and ruin MDF (or snap the bolts they provide)
* variable speed - so you can start slowly.. ensure the screw is right.. then speed up.
* size - to fit into awkward locations - I use a hex-bit flexible screwdriver extension with both my titchy ixo driver and the PSB. It should be balanced enough to have in one hand.
* impact is useful feature if you don't want to pre-drill long screw holes. Note your screws need to be able to take the high torque and so must your screwdriver bits.
* LED lighting
* magnetic bit holding - if things are going to drop down spaces.. they will.. unless it's magnetically held!
* light enough for one handed operation
* removable batteries - having multiple batteries means being able to cycle and continue...
* belt clip - useful if you're up a ladder..
