That one sounds to me like you are paying them through the nose for the privilege of doing all their leg work! If I were you, I would be getting some lessons, getting back into the swing of things, be looking like mad on sites like New Rider to see what is out there, and once you have a better idea of what you are looking for you can maybe answer some adverts, maybe make an advert yourself.
To give you a few ideas, I got my first shares by answering adverts, then put an ad out myself for the 3rd share I had:
No. 1 was a nutty TB mare her owner was scared to ride. I paid £75 a month for riding any weekday I liked. (I work shifts so could ride during the week before kids.)
No 2. was a very boring placid easy gelding on full livery. I could ride 3 times a week, including weekends, and paid £150 a month. I had all of Windsor Great Park to ride in. (I work at Heathrow, so this was pricey but handy.)
No. 3 was a gelding in response to an ad I put up in the local tack shop. He had major clingyness issues, would only hack in company. I paid £20 per week and ended up inadvertently with him on full loan for that when his owner moved abroad. He was on DIY livery and I was going up twice a day, but he was only 5 minutes down the road.
I was getting a lot of people telling me during this time (once they realised I could ride mid-week) that I could ride their horses for free, and I took various horses out to shows and hunting.
At this point I realised I could do better by buying a horse myself rather than fitting in around other people's foibles. I bought a horse and had him on livery for years, then brought him home to live in the field and stables behind our house and got a horse for my mum too. I realised with a job that takes me abroad and a child I needed a sharer. My advert asked for a competent, confident rider for 2 very large horses (mine was 17.3hh and my mum's was a substantial HW show cob.) I had a string of riders who thought they were competent, who would ride the big horse for a few months with no bother and then one day get him on one of his off days, and I'd never see them again, in spite of having described his off days to them at the start and how to deal with him!
Eventually it was a bit hard and I sold him, and my mum's horse went back to his owner. I bought a 15hh easy but young gelding, and a pony for my kids. I'd had the new horse about 6 months when an advert was sent round the riding clubs and hunts that was looking for a horse that sounded just like mine. I now have 2 adult sharers and a child who help me with my horse and pony. They pay me half the cost of shoes, nothing more, and are expected to have a lesson a month to keep their skills brushed up and my horses learning. I would have the horses anyway, and this way I can keep my horses at home and don't have to pay for help when I am away with work, and my horses are kept fit through the winter months for hunting. We all hunt, each of my sharers have been to at least one show and 2 hunt meets this year.
All of my sharers have been with me for 2 years now, and are showing no signs of going anywhere. In fact they have just clubbed together and bought themselves a project pony to keep at mine, bring on and have fun with, so now 2 adults can ride together too (and I have a pony I can borrow if I want to hack out with a family member.) So you see, you can get cheap shares, and often there is no catch. Someone who wants £200 per month PLUS bills is taking the mickey if you ask me! As I said, the project pony on our yard costs his owners about £80 per month in summer, £130 in winter. I don't charge them livery as they look after mine for me. So each half-owner shells out between £40 and £65 per month, plus their BHS/PC membership to cover them for public liability, plus a contingency amount to cover unexpected vets fees. And that is the price they pay to OWN the pony and turn up whenever they want and do whatever they want with it. I would expect a pony with bells on and golden shoes for £200 a month plus bills - my old 17.3hh highly schooled county standard show hunter didn't cost that much to keep! And he ate and crapped a lot!