Hello contrast79,
I am in the same situation as well, booked just before the Fee change for an appointment in May.
Browsed through the forum and got a few response from the past year wherein the message is people booked prior to Fee change for an appointment after the Fee change, did not pay the extra/remainder of the new fees.
Please search with the string " Old Fees" for posts between March-April 2016.
Do make sure the form you are using, the new version is out, not sure if one can trace the old version with the old fees.
https://www.gov.uk/government/publicati ... -form-seto
Please post your experience after your appointment to keep the Forum members and myself informed.
Wish you all the best.
regards,
P/S