Last year I returned to dental nursing after a 10 year break. I contacted the GDC who helped me clarify that I needed to complete my 5 years worth of CPD to be re-registered and there was a fee to pay to (this is done pro-rata if you are part way through the year already). I then re-joined the BADN and managed to find enough CPD to do my 50 hours in 3 months (hard work, but it can be done). Don't be put off by anyone saying that it's almost impossible to get back onto the register, I did it and I have since gained my sedation qualification and have been with the same practice since March last year.
Best of luck!