With new studies suggesting borrowers are spending more of their total household income on servicing mortgage debt than ever, an Englishman's home really is his castle.

In Sussex, where some of the steepest house price rises have taken place in recent years, it's also his lighthouse, bank vault and police box.

After a derelict coastguard tower in Littlehampton sold for £42,000 this week, Kim Hjelgaard rounds up some of the other unusual properties on the market.

Belle Tout Lighthouse, Eastbourne

Perched on cliffs at Beachy Head, Belle Tout is a Grade IIlisted lighthouse converted into a six-bedroom house.

It has spiral-staircase corridors, a round bathroom and 360-degree panoramic views from the upstairs "lantern room".

The property is on the market for £850,000 and whoever buys it will have a spectacular outlook on the sea and coastline and unrivalled access to nature.

There are just two drawbacks.

The location is a notorious suicide spot and the lighthouse stands at the top of a cliff gradually being eroded by the sea.

Bank vault, Hove

Built in a former bank vault with 6in metal-plated walls, this two-bedroom flat in Church Road, Hove, is thought to be the first in the city built entirely underground.

In fact, experts believe it could be the most secure home in Britain.

The flat first went on the market in January 2006 for £279,000.

Now it is up for sale again with King and Chasemore, at £365,000.

Gary Parsons, King and Chasemore's Hove branch manager, said: "It is beautiful inside.

"It is really a bachelor pad at the moment but would be suitable for lots of different people.

"We have had quite a bit of interest from young professional couples, people who commute to work and people who want to use the property as a holiday let."

The vault, which belonged to the Lloyds TSB branch that used to be based above, was bought in 2001 by Charter House Consultancy.

It teamed up with Brightonbased architect Peter Overill Associates to design the flat.

A safe and a lift had to be removed and the walls had to be knocked down and rebuilt.

Former Evangelical Church, High Street, Worthing

In Worthing town centre, this former church is zoned for commercial purposes only and currently operates as a bar/restaurant.

But with the seller open to the idea of splitting this enormous property into separate units there is scope for the space to be put to creative use.

It is conveniently located on the east side of the High Street opposite the Guildbourne shopping centre multi-storey car park.

But with a £900,000 asking price it's not exactly a bargain.

Police box, Brighton

A former police box on the corner of Stanford Avenue and Ditchling Road, near Fiveways in Brighton, sold before it even went to auction.

The guide price for the 10m (33ft) by 13.7m (45ft) building was between £70,000 and £90,000.

But, if history was to repeat itself, investors could fork out twice as much.

The same police box was sold in 2004 for £92,000 and another in Margery Road, Hove, just off Old Shoreham Road, went for £71,000.

They were advertised to go for between £30,000 and £50,000.

The businessman who bought the boxes intended to use them for storage, office facilities and development.

The box was released by East Sussex County Council on the instructions of Sussex Police Authority in 2004.

Police records show it was built about 55 years ago and used as a base for beat officers.

It has running water, phone lines and electricity.

Earthship, Stanmer Park, Brighton

Like most out-there ideas, Earthship homes are the idea of an American, in this case architect Michael Reynolds.

Essentially, they're built from yesterday's rubbish, which in the case of the Brighton Earthship at Stanmer Park means old tin cans and tyres.

The Stanmer Park prototype was completed in February and will be used chiefly for corporate functions and private parties.

But if all goes to plan, the Earthship housing scheme approved on a prime 1.1-hectare site overlooking Brighton marina is property development with a difference.

Fifteen thousand tyres are expected to be used in constructing the 16 dazzling eco homes, which will all be fully sustainable and independent from the grid.

It is estimated that the homes could go on sale at between £250,000 and £400,000, a very reasonable cost for no-bills housing on a prime location.

Six homes will also be allocated to housing associations.