Blame Griff Rhys Jones and the success of his tele-vision series Restoration, spiralling house prices or plain homeowner greed, but the British appetite for wrecks, ruins and dilapidated shacks of all shapes and sizes knows no bounds, even though they are becoming increasingly rare and expensive. So, how can you bag a bargain ripe for restoration, other than by endlessly trawling estate-agency windows or hunting them down on foot?

Enter the architectural conservation charity Save, which next week publishes its annual catalogue of what it deems the 100 most interesting period buildings in danger of being lost. Called Opportunity Knocks, it features derelict, vandalised and forgotten castles, cottages, barns and breweries; some are Grade II-listed, while others have no listing at all. The Sunday Times has been given an exclusive look.

Only about one in 10 of the properties, drawn from Save’s broader, 750-strong Buildings at Risk register, is for sale in the conventional manner through estate agents. One of these is a Victorian former Methodist chapel in Alston, Cumbria, England’s highest hilltop town, 1,000ft above sea level. It is for sale for £500,000 through Pennine Ways, 01434 381808, www. countrycottages.net). Another is an old railway station building in Frodsham, Cheshire, which is available on a 50-year lease for a nominal rent (Spacia, 0161 838 1236).

In most cases, however, the register gives only contact details for a council conservation officer or other local official involved with the buildings. They should then help to liaise with the owner, but it can be a complicated process — the reason some buildings have not been sold is that nobody knows who owns them.

Take Thorington Lodge, a Grade II-listed Georgian property near Saxmundham, in Suffolk, that could be converted into a charming three-bedroom house. Save says that the owners are prepared to sell, but a price has yet to be fixed and no agent has been appointed. Adrian Craddock, the council conservation officer, has more details (01394 444474). Craddock also knows of a picturesque 17th-century timber-frame farmhouse in Peasenhall, near Framlingham, available to buy on a very long lease.

Sandra Jones, a conservation officer for Powys council, meanwhile, is looking for a new owner for a 17th-century farmhouse at Moydog, near Welsh-pool. The interior has a large gable fireplace with an iron range and side oven, while the rooms have a mass of original wood features, including chamfered spine beams and timber-frame partitioning. The property, says Jones, “ticks all the right boxes” when it comes to Welsh rural idyll. The only problem is that it will take a little research to work out who owns it. Interested? Contact Jones on 01938 551000.

Other highlights on the list include an overgrown lodge in Yorkshire and a row of Georgian terraces in Liverpool, also in need of rescuing.

David Plaisant, buildings-at-risk officer for Save, says that inquiries have doubled over the past five years. “Everyone is looking for a hidden treasure,” he says. “Anyone who travels round Britain knows there are many beautiful buildings empty and decaying that could be given a new lease of life.

“We now get 20 or 30 calls a week looking for more information on the properties that are featured on the register, and 500-1,000 hits on the website every day. We want to show people the first step, and want to persuade owners to offer the buildings for sale on reasonable terms.”

Plaisant says that the calls are not just from architecture enthusiasts out to save our rich heritage. Increasingly, the motivation behind many of the restorations is the British housebuying public’s apparently insatiable appetite for making money out of property. But he warns that none on offer are a “splash, dash and cash” option.

Steve Crockwell, 55, can confirm that. When he visited the Cambridgeshire village of Yax-ley five years ago, he spotted a tumbledown, decaying cottage, covered with a tarpaulin, on the way to the pub. He asked the landlord, who called over the owner. Crockwell struck a deal on the spot to buy it for £122,000.

Today, he and his girlfriend, Jane Maxwell, 53, live in the immaculately restored three-bedroom property, which was valued last year at £320,000. But it was hard work, even though Crockwell, a developer who specialises in listed buildings, knew what he was doing. He spent about £80,000 and 20 months stripping paint and wall-paper and restoring the cottage to its original glory, even importing the right reed thatch from Poland to redo the roof.

What advice does Crockwell have for anyone wanting to tackle a restoration project? “You should expect trouble,” he says. “And it can be expensive. Then again, you’ll have gained the house you want.”

The Opportunity Knocks catalogue is available for £12 (members £10) from Save Britain’s Heritage, 020 7253 3500, www.savebritainsheritage.org

Times recommends

• Second homes: credit crunch casualty or money-spinner?
• How I built my own sliding house
• Top 10 incentives for house buyers