The Celebrity Eclipse carried back some 2,200 stranded travellers
Hundreds of Britons caught up in the ash flight ban remain stranded at Bangkok's airport as anti-government protests take place in the capital.
The tourists have camped out at Suvarnabhumi Airport in the hope of catching flights home.
The Foreign Office advised against non-essential travel to Bangkok but said the unrest did not affect the airport.
Meanwhile cruise ships returning stranded Britons have docked at Falmouth and Southampton.
More than 2,000 people were on board the £500m luxury liner Celebrity Eclipse when it arrived following a 30-hour journey from Bilbao in northern Spain.
Those with furthest to go were allowed to disembark first.
Passenger Alice Hoon said her family had been stranded for four days in the Algarve but they still had an 11-hour journey ahead of them to get home to Oban in Scotland.
She said: "We took the option of the ship because we had to get back as our children have exams," Mrs Hoon explained.
Earlier, more than 1,600 people who were stranded in Madeira arrived at the port of Falmouth in Cornwall on board another Thomson cruise ship, Island Escape.
Meanwhile, some passengers stranded in Bangkok spoke of a "dog-eat-dog atmosphere" as fellow tourists scrambled for valuable flights home.
Ellen Pike from Letchworth said she felt the government was not doing enough to help.
"This was a serious situation last week, but now that the central area of Bangkok has been taken over by protesters and violence has escalated, it is now paramount that all stranded passengers are repatriated."
A change in wind direction has forced Iceland to close its main airports for the first time due to the danger posed by the ash cloud.
Until the threat passes, Glasgow Airport will act as a short-term hub for Iceland's national carrier, Icelandair.
Meanwhile, British Airways has rejected suggestions it is prioritising new passengers over those stranded abroad.
Some passengers have complained that BA appears to be selling empty seats to new passengers on earlier flights.
Travellers have camped out in a bid to secure a flight back home
However BA said these were being offered at very high prices to keep them empty on its computer booking system, so the stranded passengers can be slotted in.
BA and Ryanair have said they will be flying extra services over the weekend to get more passengers home.
Flights have also resumed at airports in the Highlands and Islands, with Inverness, Wick, Kirkwall and Stornoway airports reopening for business.
The Department for Transport said restrictions on night flights to and from Heathrow, Gatwick and Stansted had been relaxed on Wednesday and Thursday night to clear the backlog.
The European air traffic agency Eurocontrol said European air traffic had returned to normal, with 29,000 flights expected on Friday, the Reuters news agency reported.
The Association of British Travel Agents said it expected its members to repatriate more than 100,000 passengers this weekend after UK flight restrictions as a result of a volcanic ash cloud from Iceland were lifted.
Meanwhile, RAF Typhoon jets are flying again after being grounded by fears over volcanic ash. The Ministry of Defence said engineers had checked the planes and were satisfied they were safe to fly.
On Thursday more than 80 people were injured after clashes between anti-government protesters and riot police in the Silom business district of Bangkok.
Early on Friday, hundreds of riot police crossed a major road to confront red-shirt anti-government protesters.
Reports had said that three people were killed, but the government later said that one person died.
With unrest flaring in the city, Emma Stubbs told the BBC that the mood in the airport was "dog eat dog" as travellers camped out to secure a flight back home.
She said: "We have heard of other passengers who have lied - making up sob stories - so they get prioritised over the rest of us who are stranded."
The Foreign Office said Britons "should exercise extreme caution throughout the country".
However, Quinton Quayle, the UK ambassador to Thailand, told BBC Radio 5 Live that there was was "no security issue" at the airport and embassy officials had been providing advice to travellers.
Engineering work on the East and West Coast Main Lines between London and Scotland was cancelled to enable more direct services to run.
The eruption of the Eyjafjallajokull volcano in Iceland from 14 April sent vast amounts of ash into the atmosphere.
There were fears the ash could pose a risk to jet engines but flight restrictions were lifted on Tuesday night after regulators tested the impact on aircraft.
The cost to European tourism has been 1.72bn euros (£1.49bn), according to a World Tourism Organisation estimate reported by the AFP news agency.