Raoul Fraser, of luxury holiday park operator Lovat Parks, said: “The cost is £3,000 to £5,000 for a high-quality wooden hot tub and, while it takes a lot of management, you should expect it to pay you back within a couple of years.”

Good garden furniture and a barbecue are big draws, said Gemma Maclaran, of buying agency Middleton Advisors. Also consider providing Netflix and Sonos wireless speakers – these could add 5pc to the amount you can charge, said Paul Clarke, of Mr and Mrs Clarke estate agency.

6. The devil is in the detail

Luxurious properties can attract 10pc more bookings and earn 70pc more revenue, according to Cottages.com.

Think fresh flowers, padded coat hangers, cookery books, board games, luxury food hampers and a bottle of fizz on arrival. Hotel-style lifestyle imagery with staged dining tables will also help you stand out and charge more per night, according to Sarah Ward, of design firm Ward & Co.

7. Home – but better

The point of a holiday is to come back feeling refreshed, so focus on the bedrooms, said Sian Elin Thomas, of interiors brand Sian Elin. “Invest in a comfortable mattress, buy high-­quality bed linen and make sure blinds or curtains are blackout.”

Frances Russell and her husband recently renovated an old coach house on their Isle of Wight property. “The plan was to bring in money to put towards renovating the main house,” Mrs Russell said. The coach house has been booked for 25 weeks this year. It costs from £600 to £1,250 a week and is on track to make £22,000 a year, almost half the £50,000 cost of the works.

Mrs Russell attributed the success to a careful balance of economy and luxury. She bought designer fabrics on eBay and found an £80 sofa that she had re-upholstered.

“There’s nothing more depressing than going on holiday and seeing that everything is from Ikea,” she said. “It has to be nicer than being at home.”