Kev, good idea to get that radio, it will help - although I'd not expect an immediate improvement, it will take a few weeks. I assume you'll get a hand-held, that way you can use it in the car etc as well & become a little more used to doing other things at the same time.
My suggestion would be that you also interact with the [radio] traffic at the same time - there's not a lot of point just listening, try to envisage your response to a query you hear or how you'd make a call etc. This will greatly accelerate your learning & assist you in being more comfortable next time you're in the 'plane
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Finally there's nothing like practice. In this situation you're flying a 'plane which in the early stages of learning (ie. up to PPL and a good few hours beyond) is not an autonomous motor-skill. In other words you really have to think what you're doing and your actions are deliberate rather than automatic. This will tend to mean that your radio work shares that thinking time with your flying work - when you become more used to one and/or the other there's less thinking to do & so the other task(s) will also become easier because they have more brain-time available. Everthing improves markedly from there & you'll wonder what all the fuss was about - but it will take time & practice, just as it does for everyone and particularly for you where you're spacing out the flying side of things, this means of course than it'll just take longer for some things to become automatic. If you get the radio - and _learn_ from it rather than merely listening - then that'll also help the flying itself because you'll spend less time thinking about the calls & how you're going to respond.
Incidentaly I agree with Bigglesthefrog, be conversational insofar as it's easier and more relaxing to simply communicate your intentions rather than getting all stressed about procedure but at the same time be concise/short if you can. The procedure will come in time and slight informality is no real issue as long as it's clear what you're doing or responding to but no-one appreciates it when someone reads an essay over the air
FP.