Holidaymakers and others arriving at Birmingham Airport on Tuesday said they had been unable to catch earlier lights before the new rules kicked in.
Travellers were told by Government chiefs they must arrive in the UK before 4am on Tuesday, or they will be forced to self-isolate at home for 10 days.
Health Secretary Matt Hancock said the controversial move was needed to protect the "progress that we've made" amid reports of rising cases in Portugal.
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Matt Parsons, from Halesowen, arrived at Birmingham Airport on the 10.25am Ryanair flight from Faro – having came back for five days to see family and friends.
The 28-year-old said: "I've been living in Portugal for two years, so it's the first time I've been back since 2019 – I work out there for AirBnB.
"It's been a nightmare [getting back], to be honest – I had a girlfriend in France and I flew there three times in the height of the pandemic, but it was fine, but coming back here was harder.
"I looked for earlier flights but they pretty much tripled in price – about 300 Euros to change the flight – and now I have to self-isolate for 10 days. I'm back to see family and friends, have some breakfast and maybe even a roast dinner."
Andrew Grubb, from Redditch, had visited Faro with his wife and two kids – along with his friends in their two children – and they will now have to self-isolate for 10 days under the rules.
He said: "I'm pleased to be back in one respect, but not very happy – it's a disgrace, if I'm honest. We had two days [before we found out] and it put a dampener on it rally, friends who booked to come out were messaging us about it.
"It's been nice to get the kids away, which was something, but I have to say the people in Portugal were going mental – one lady, an Uber driver, was in tears because she had to give her car back because she couldn't afford to pay for it.
"The rate over there is lower than what it is here – they've got a problem in Lisbon but not in Faro. It's been great out there, they've got really good restrictions and everyone felt really safe – there was no problem at all.
"We looked [at getting earlier flights] but it would've cost us a fortune with the kids and we've spent about £1,000 in tests – I need to get back to work so I have to get a five-day release test."
Mr Grubb claimed the country had done over 100,000 tests – and only had six positive cases – which led to him questioning the decision. He added: "They've done over 100,000 tests over there and there's been six positive cases. I really don't get it. The Champions League final there were two English clubs travelling there – and fans – and that was fine. I just don't understand it."
Government chiefs say people who return from amber countries, who can't afford to self-isolate for 10 days, can apply to pay for a private Covid-19 test under the Test to Release for International Travel scheme, with people allowed to stop quarantining – after spending five days in England – if the result is negative.
Zoe and Wayne Parris, from Erdington, said they were unable to change their flight to before the restrictions hit due demand soaring as people tried to rush back home.
Zoe, aged 46, said: "We did look for flights, but there was none available. On Monday you could notice a big difference [in Portugal] – it was really busy and now it's like a ghost town there.
"We had just landed when we found out the news and we were really disappointed, but what can you do?"
Wayne, aged 50, added: "It's been a bit of a financial worry for us [due to the cost of testing] and plus it's 10 days off work, as well, and it all happened so quickly."
Simon and Jackie Robinson, from Wellesbourne near Stratford-on Avon, had been due to arrive on Tuesday – but they tried to catch earlier flights, which they were unable to do.
Jackie said: "We found out on day two – it was very sudden and I spent a long time trying to find out what the various tests we could get were. And Portugal are furious about it – their rates are lower there than what we have now."