Widespread disruption is expected on Wednesday after the storm swept across the country overnight carrying heavy rain, hail and dramatic thunder and lightning.
A man was injured in Hensol, the Vale of Glamorgan, south Wales, when a tree fell on his car, the Welsh Ambulance Service said.
Paramedics were called to Hensol Road at around 10pm on Tuesday, where they took the injured man to the Royal Glamorgan Hospital.
Tens of thousands of homes and businesses across the Republic of Ireland and Northern Ireland suffered power outages as they bore the brunt of the storm.
They included 55,000 properties in the Republic and 20,000 customers in Northern Ireland.
Around 2,500 properties between Cornwall and the Midlands were also blighted by power outages, largely due to flying debris, Western Power Distribution said.
There were roughly 60 incidents reported as Storm Eleanor barrelled across the network overnight, with Mid-Devon experiencing the worst damage, according to a spokeswoman.
Several major bridges were closed due to high winds and there were numerous reports of fallen trees blocking roads including the M25.
A tide-battered harbour wall in Portreath, Cornwall, partially collapsed as the storm intensified on Wednesday morning.
Cornwall Police said they were called at around 5.50am due to a very high tide and water coming on to the road.
Closer to shore, cracks began to form in the harbour wall and water poured through it, while some steps collapsed.
A spokeswoman for Cornwall Police said a 25ft to 30ft section was later knocked down further along the wall, but added there was no risk to anybody.
Overturned vehicles forced closures on the A1M near Hatfield in Hertfordshire, the M6 near Lancaster and M5 near Worcester, where a recovery operation was required to clear up the contents of a lorry left spilled on the road.
An object in overhead lines between London Paddington and Hayes reduced the number of trains leaving the major hub, while power outages halted rail services between Letchworth Garden City and Cambridge.
A yellow warning of wind remains active for all of England and Wales, most of Northern Ireland and the Scottish Borders until 6pm on Wednesday after an amber warning was put in place for the early hours.
The Met Office said gusts of 100mph were recorded at Great Dun Fell in Cumbria at 1am, while wind speeds reached 90mph at Orlock Head in Northern Ireland on Tuesday evening.
Gusts up to 89mph were recorded on the Isle of Wight at around midnight, while in Northolt, north-west London, speeds of up to 73mph were detected and 77mph gusts were recorded in High Bradfield, South Yorkshire.
Meteorologist Becky Mitchell said the risk of more "violent storm-force gusts" had lessened, although wind speeds of between 70mph and 80mph could hit some parts.
"Storm Eleanor has swept through and the eye is now crossing the North Sea, although there will continue to be strong gusts through the day," she said.
"We have seen some heavy showers push through across the south of the UK along with hail, loud thunder and lightning, which has woken people up.
"It is possible there will be quite widespread disruption this morning and it is worth checking before you travel."
The Severn River Crossing and the Orwell Bridge in Suffolk were closed in the early hours due to strong winds.
Highways England said there was a possibility that the Queen Elizabeth II Bridge would have to close and the east tunnel of the Dartford Crossing had been shut in case it had to take diverted traffic.
Police forces in Cumbria, Suffolk, Norfolk and Humberside were among those to issue warnings that downed trees had blocked routes.
Isle of Man Police said infrastructure staff worked through the night to remove trees from the roads, while there were multiple reports of roofs coming off buildings, flooding and mud debris.
The States of Jersey Police said multiple roads remain closed due to fallen trees, stormy weather and high waves.
As well as the problems posed by high winds, the Environment Agency has issued 46 flood warnings and 115 flood alerts, with coastal areas under threat from a combination of a high tide and large waves.
In Cheshire the RSPCA was called to a road in Poynton where a swan had taken up residence in a puddle, blocking traffic.
The Thames Barrier was being closed to protect London from swelling tides brought on by Storm Eleanor.
Measures to bring the defence system into action were planned for around 10.15am, it was announced on Twitter.
Increasing surges were forecast after high tide in the afternoon, triggering the precautionary move.
It is the 180th time the Thames Barrier has been closed to guard the capital from tidal flooding, according to an account run by Environment Agency staff at the site.
A falling tree injured two men overnight when it crashed into their car, Hampshire Police said.
Officers were called to Lyndhurst Road in the New Forest at around 3.20am, and both occupants of the Ford Focus were taken to hospital by ambulance.
The road was cleared by 6.43am, according to a spokeswoman.