To give some figures, I am in the Midlands.
My livery bill is £500 a month and includes hay, trailer parking and basic care, so turn outs, bring ins, rug changes, mucking out and giving hay/feed. It doesn't include bedding or feed or riding or grooming.
My bedding works out at about £14 a week but that is on a pretty cheap woodchip bedding bought by the pallet load. If I was buying nice shavings in small quantities in would be more like £20 a week.
Farrier costs depend on your horses needs, I put a lot of effort into barefoot so my farrier costs are low, about £45 every couple of months but a full set of shoes is more like £80 and can be over £100 when you start adding things like pads, stud holes, or special shoes.
Dentist twice a year at £45 a time. Physio once a quarter at £55 a time. Worming about £30 twice a year, plus the cost of worm counts. Vaccination about £50 a year.
Feed and supplements, if you are lucky perhaps £20 a month, but easily £50 or £100. I haven't worked mine out.
Insurance about £90 a month.
Lessons around £30 or £50 a time depending upon the instructor and whether you have to hire a school.
Saddle fitter about £50 twice a year.
Clipping £30 - £50 two or three times a year.
Then you have to allow for any hoc vets bills, and purchase of equipment. A new saddle will easily set you back £1000. A waterproof turnout rug £100, a wheelbarrow £60, but even small stuff like haynets and antiseptic cream need to be purchased for the first horse and need replacing regularly.
Take into account that a big bill can hit at any time. Vets bills aren't predictable, but avoiding incurring them inevitably ends up more expensive in the end.