Criminal sanctions for breaches of REMIT Articles 3 and 5 (use of inside information and market manipulation) will come into force on 13th April, following the passing of the relevant legislation, which can be found here.
The rules mean that the UK joins some other countries with a stricter set of penalties for breaches of REMIT. Civil sanctions came into force in the UK in June 2013, in line with the timetable intended as part of the European wide roll-out.
Member states have been variable in bringing in legislation, both in terms of the timetable and the level. A small number of authorities have yet to implement any legislation. Many others still have only penalties, rather than jail sentences, available.