I started to be given radio work after about fifteen hours or so. The workload does increase but I think it is a neccessary part of your training. I don't know if you can do a first solo without radio, I trained at Coventry and I don't think that I would have been allowed to complete a circuit without it.
There are frequently the occasions when you ask your instructor what was said..it seems to me that the ear becomes more attuned as time goes by, I found it useful to write as much as possible down on my knee pad.
Longer transmissions when being given a squawk, a QNH and then being asked for your altitude and position all at once can be quite daunting at first but it does seem to become a task that is just part of the routine the more it is practised.
There are some ATCs that are quite difficult to understand, and some who are very clear and concise...maybe this is down to their own mic's, maybe some of them mumble a bit.
A lady of shorter stature who was also training at the same time as me had problems setting QNH and QFE due to the students right side seating arrangement, she overcame this by slipping a short piece of garden hose over the altimeter setting knob!! ...not sure if this would be a Robinson approved modification though.
Hope this helps
Micky