How can they regulate their spending?
Not waste money in the first place. A town near us got a shiny new health centre under Brown/Blair. It's a 3 story huge building that replaced a small GP surgery/health centre. The top two floors have never been used. The GPs and district nurses etc work out of the ground floor along with other services such as diabetic eye checks one day per month. When it was planned/opened, it was supposed to have a minor injuries unit, xray, small operating theatre etc - by the time it had been built, the local trust decided to beef up the nearby city hospital instead and the town health centre floors weren't needed anymore. It's that kind of money wasting that needs to stop.
Their procurement is also flawed. They vastly over-pay for basics that could be bought for a fraction of the price. One of my clients is an office supplies firm. Each year they produce a catalogue which has crazy high recommended prices. They then make the procurement managers think they've negotiated a fantastic deal by offering, say, a 50% discount for particular customers, like GP surgeries or a hospital dept., but in reality, no one in their right mind would ever have paid the full RRP. They say it's all part of the game - the procurement manager can trot off to trust board meetings to tell them how wonderful they are to get a 50% discount, the supplier is still profiteering even with a 50% discount because he's given higher discounts to everyone else to compete with the likes of Amazon etc.
A few years ago, the staff on just one ward at our local infirmary saved around £50k per year by shopping around to buy their own non-clinical supplies. That's just one ward, and saved by "normal" people. It was in the local paper and the figures were confirmed by executives no not "gossip" or fake news. If that could be replicated, it could save tens or hundreds of millions. Trouble is, NHS staff don't seem to care about the small things, but the small things add up!