The CAA website seems to suggest that the instructor needs to email an SRG1157
If revalidating via experience (including your one hour coaching flight) your instructor should email the 1157 to the CAA after you've signed it. Of course, you can agree on who does it but the bottom line is that it's the instructor's responsibility to send it. It's yours to check it's been done.
I renewed my licence last month and followed that process.