Depends what you class as gravel rides. If it’s usual routes but on a gravel bike so a mix of short sections of tarmac, very muddy bridleways, lots of slick tree rooted forest, sandy field edges, canal towpath, wooden steps, gravel double track, slick clay cut throughs, draggy grass and moorland and trails the local MTBers have built in the woods then there’s a lot of scope from Kings Norton out to Worcester. If it’s gravel rides in the American sense of long forest road type stuff then there’s not a lot.
There’s a few west midlanders on the UKGRAVELCOLLECTIVE Facebook page, might worth posting there too https://www.facebook.com/groups/1398829490247760/