I would have thought that you have a good chance of being offered in the first round...... if not then shortly afterwards.
This is from a previous post.
It will most probably be about the same cut off for first round offers.
Herschel may be slightly higher as it seems to be becoming more popular.
I think last year the last info we were given was..
LG 116 (some 115)
HG 113 (some 112)
SG 112 (some 111)
this is only by memory.... if I come across anything diff or someone else can correct me then I will edit the post.
Since then (in the ombudmans report into appeals as Herschel) eventually some 111's were offered a place at HG.
Slough Grammar 1st round was 113 last year apparently.... but as they are the only one including the Maths this year it may make some difference......you can't tell.