Of course the CAA can make the £73 charge approved by the Secretary of State;
The Civil Aviation Authority, pursuant to Section 11 of the Civil Aviation Act 1982 and after consulting the persons who, in its opinion, are likely to be affected by the Scheme or such of those persons as it thinks fit, and after consulting with the Secretary of State, hereby makes a Scheme for determining the charges to be paid to the CAA in connection with the performance by the CAA of the following functions:
If you have not applied for the EASA PPL by April 2018 depending on the rating you have SSEA or SEP, your privileges will be restricted to the UK only. Which means no EASA recognised aircraft.
Any ratings that are current and valid will be transferred onto the EASA licence. You must apply though. Do not rely on the CAA to transfer automatically ANY of your ratings. No additional charges will be made for current and valid ratings. A charge will be made for rating applications at a later date. Any ratings not valid at the time of applying will be entered onto the back of the licence as non valid until renewed. DO not forget to list all ratings valid or not to ensure they are recorded on the licence.
It is pointless to delay applying for it is a one off charge for a lifetime licence. DO NOT TEAR UP YOUR UK LICENSE keep it valid alongside your new EASA licence (LAPL or PPL)