Thank you for your responses, I really appreciate your support.
I have called CAA to clarify and they confirmed the following:
1. I need to fill both forms SRG1126 (Application for a Night Rating) along with SRG1104 (conversion from JAR to EASA).
2. I need to pay both fees £89 (Application for a Night Rating) and £73 (conversion from JAR to EASA) in addition to £6 (courier fee). Total £168.
3. Within SRG1104, Night Rating details can be written in either section 5 (Ratings held) or section 7 (Conversion of additional ratings) - I will probably write in section 7 as the level of detail required seems more appropriate for the Night Rating.
New questions relating to SRG1104 section 9 (Flying experience)
All my flying has been in single-pilot aircraft (C-152, C-172, PA-28 and the likes); in the capacity of P1, P1S or PUT. For single-pilot aircraft, the form only asks for time as Pilot In Command (P1). Does this mean I do not need to state my dual time (with an instructor) at all?
Also, does P1S count towards P1 time?
Thanks again for helping me along this journey!