The OTC does not trade after hours. What you are seeing in the "after hours" (post 4:00pm) are protected "T" transactions.
A protected transaction occurs when a large order is going through the market. The buyer (or seller) may wish to keep the order anonymous from the rest of the market as the size of the order could greatly alter the price of the stock. With a protected transaction, the dealer will put the trade through in small quantities rather than knock the whole order out in one hit. The entire transaction is reported once the deal is completed. The LSE is notified at the start and at the end of the transaction. However, the market as a whole isn't told until the end, thus the order is protected.