Solo travellers also routinely report being allocated substandard rooms compared to couples. On a recent coach holiday to Wales with Shearings, Elizabeth Knowlson said she was left with a dirty room which has a bucket outside the door to catch leaks from the ceiling. Though the company did offer her a new room, it was a small single. 

She told Which?: “I could simultaneously touch the opposite walls with outstretched arms. I don’t mind paying a single supplement, but this room was only fit for one person.”  

Shearings said it "proactively seeks accommodation with low or no single room supplements for our guests, and only ever charge a supplement if a hotelier imposes this charge to us as a company."

Commenting on Ms Knowlson's case, a spokesperson added it was "disheartening" that she accepted the second room but remained unhappy, and that any concerns should have be raised with hotel staff so they could be resolved. The company has since announced that it has plans to remove single supplements in as many as 27 of its UK hotels.

As well as being overcharged and undervalued, solo travellers also face more limited choice when it comes to holidays. Which? found both Jet2holidays and Tui had notably fewer offerings for solo travellers – 10 per cent fewer in the case of Tui, and 20 per cent for Jet2.

However, it’s not all bad news for those travelling alone, as there are a number of tour operators who specialise in solo travel or don't penalise those heading out alone. Below, we highlight the travel companies to consider when booking your next solo adventure. Some offer specialist singles holidays, others have departures with no single supplement or help customers avoid the charge by arranging same-sex room shares.

There are always more women than men travelling on these trips: usually 65:35. Everyone who joins a tour has their own en-suite room, which is usually a double for single occupancy.

Friendship Travel (0289 446 2211; friendshiptravel.com) House party-style beach holidays in Greece and Majorca taking over small hotels entirely. A Friendship host is always on hand to ensure no one is left out. Group size is around 20, most aged 35-60. There’s also a range of short breaks and long-haul options including the Caribbean, Mexico and Cambodia.

Just You (0800 112 3311; justyou.co.uk) An impressive portfolio of holidays, from Cotswolds weekends to Antarctic adventures, plus culture-and-chill weeks in the Mediterranean. Most holidays are led by a British tour manager. Group size is up to 30; fewer on long-haul trips but always more than 12. Age spread is 35-70.

One Traveller (01760 722011; onetraveller.co.uk) Aimed at the over-50s and escorted by experienced British hosts. Suggests first-timers try a break in Budapest or Prague. Maximum group size is 25. Long-haul options include Sri Lanka, China and North America.

Solos (0844 815 0005; solosholidays.co.uk) More than 35 years’ experience organising singles holidays worldwide, including cruises. There are four age bands, and minimum group size is around 15 with a 60:40 female:male ratio. Runs its own hosted ClubSolos holidays in Greece, Majorca and the Algarve.

Activity and adventure 

Adventure specialists attract a mix of couples, friends and singles who travel, sightsee and take meals together. Most offer same-sex room shares or affordable supplements for your own room.

Contiki (0808 281 1120; contiki.com) A big choice of holidays worldwide for 18-35s, from Greek island-hopping to new tours of India. Group size varies from 30-50; a mix of nationalities, most with English as their first language. Travel by coach with a Contiki tour manager organising activities and sightseeing.

Dragoman (01728 861133; dragoman.com) Focuses on overland camping, travelling in a converted lorry, on trips ranging from 10 days to four months. South America and south-east Asia tend to attract the under-30s; adventurous 60-somethings might tackle the Silk Road and North America.

Explore (01252 883963; explore.co.uk) More than 400 tours worldwide, from leisurely explorations with beach time in Europe to treks up Kilimanjaro. About half of its customers are travelling solo (60 per cent females), mostly aged 30-65, though the more expensive trips attract the 50-plus. 

Wild Frontiers (020 8741 7390; wildfrontierstravel.com) Ground-breaking itineraries worldwide for groups of up to 12, many of whom come solo. Wide age range, from 30-70, mostly well-travelled professionals. Activity

Spice (0161 873 8788; spice-escapes.co.uk) An organisation of activity clubs with a membership largely comprising singles aged 35-55. A big choice of adrenalin-fuelled days out as well as chill-out weeks in Turkey and the Costa Blanca.

ATG Oxford (01865 315678; atg-oxford.co.uk) Runs superb walks with top-class food and hotels in southern Europe.Ramblers (01707 818388; ramblersholidays.co.uk) Has well-priced walks worldwide for groups of up to 18 with no single-supplement options. Also an Adagio programme for those who prefer gentle walking mixed with sightseeing.

On Foot Holidays (01722 322652; onfootholidays.co.uk) Can organise walks for those who prefer to walk alone (luggage transported) all over Europe with low single supplements.