First of all you must appreciate that it is not you that is pilot in command when you are doing your CPL training, it is your instructor, therefore whether you have an IMC or not is irrelevant.
There is no problem with doing training VMC on top, however, it depends on what exercise you are doing. Instrument flying and some aspects of general handling can be done on top, however, you would be wasting your time if you were doing PFL's or VFR navigation.
The only way that you will eliminate hold ups due to weather is to do the training in a country with favourable weather patterns. Mind you if you start your training now, you have the summer to get it done.
All the best.