[CherryBrandy]

hello there HaylB, yes all good advice. In West Yorkshire you probably don't need a fridge though if wish to save a little money on the 'ol electric. Horsfields are very good hibernators I have found and they will stop eating towards the end of August, even sometimes if indoors, so rule of thumb , stop feeding for a month when weather (temps) are warm enough for all food to pass through, then over 3 - 4 weeks further depending on size of Tortoise they should be purged. It's stating the obvious but if you feed tortoises and they do eat (like piggy little Horsfields do as they buck the trend), and then the temps drop the food won't pass through enough or in time, temps don't rise again and the food will rot inside the tortoise, blow up, and the gases and toxins will kill him. Sooooo make sure the temps are enough for the food to pass through, not too high they expel energy, or too warm they dehydrate (so consider bathing prior to boxing up, though in over 25 years I have never once bathed my Horsfields prior to hibernation, but I do keep a 'weathered' eye).
Then just let them naturally slow down and you should know when it's time to wrap them up or fridge hibernate. My usual aim is everyone away first week in November. Weighing is best practice too so you can keep an eye on whether the bladder goes, or they lose too much weight. Check weekly, I prod and probe my on their back legs for retraction. If in fridge - daily - to let in oxygen. Tortoise hearts beat around once every three minutes (or is it 3 times every minute, a quiz for you...) so it's not critical if you miss a few hours. If naturally hibernating or in a box then it's easier to see when they stir and begin to wake. Fridge is more controlled so benefits on both.
I love the fact my lot come out all on the same day as each other in a row - you know usually spring is here then or rule of thumb again the temps have reached 12 degrees 3 days in a row. Don't be scared , it sounds worse than it actually is - I would say trust in the judgement of the tortoise but don't give Horsfields food as they will gobble it down usually, CB