If you want to apply for an active substance approval, you have to submit your application in an EU or EEA country. 

Supplier of biocidal substances or products

Under the BPR, substance or product suppliers of biocides have to either be located in the EU or have an appointed EU-based representative to be listed in the Article 95 list of substances and suppliers. Non-EU companies are included together with their appointed EU representatives.

Non-EU companies listed under Article 95 of the BPR and with an EU representative located in the UK will also need to get a new representative within the EU.