European Patent Office (EPO)
The European Patent Convention is not an EU agreement and the EPO is not an EU body. The EPO contracting states include a number of countries outside the EU, for example Norway, Switzerland and Turkey, and the UK will remain a contracting state of the EPO after it leaves the EU. A European patent attorney in any of the EPO contracting states has the right to represent clients in the EPO and before the Boards of Appeal. So UK counsel will still be able to represent clients before the EPO.
The Unitary Patent and The Unified Patent Court (UPC)
The arrangements for a Unitary Patent and a unified Patents Court were due to come into effect about halfway through next year (2017). Under these arrangements, it will be possible, upon grant of a European Patent by the EPO, to designate a Unitary Patent which would cover up to 26 UPC countries i.e. countries of the EU which have joined the UPC system. It will continue to be possible to validate a European Patent individually in the EPO contracting states. The Unified Patent Court will have jurisdiction over both Unitary Patents and (subject to transitional provisions) European Patents validated in one or more UPC states. All European Patent Attorneys having a relevant additional litigation qualification will be able to represent clients in the UPC regardless of whether they practice in an EU or UPC state. So clients will still be able to use UK counsel with respect to the Unitary Patent. Note, however, that because of the UK's decision to leave the EU it is probable that the coming into force of the arrangements for the Unitary Patent and the UPC will be delayed.
European Union Registered Trade Marks and Registered Designs
Despite the decision in the referendum, the UK will remain a member of the EU for several years while negotiations for the terms of its withdrawal take place and are completed. During that period it will continue to be possible to obtain EU registered trade marks and registered designs through the EUIPO (formerly OHIM) and these will continue to cover UK. After UK withdraws from the EU, protection for trade marks and designs in UK will need to be applied for separately at the UKIPO, and protection for the remaining EU countries may be obtained through the EUIPO. The UK government will make arrangements for EU trade marks and design registrations to continue to have effect in UK after the date of UK's withdrawal from the EU. So clients' existing EU-based trademark rights will continue in full force and effect in the UK.