Thames, Severn, Trent, Clyde, Mersey.
Probably because the UK isn't a particularly large country (or group of countries). No matter where you are in the UK, you are never more than 150 miles from the sea - which may account for the rivers being relatively small. rivers such as the Nile or Amazon have travelled thousands of miles from their source to the sea.
There are 32 rivers in the UK! including the Thames and Trent which is the largest in England
Only on very large rivers, such as the River Avon.
there are 32 large rivers in Iraq but the biggest one is Euphrates
The Clyde, the Severn and the Avon are but three of the rivers in the UK.
Rivers
The rivers Severn, Thames, Trent and Great Ouse.
Rivers are coloured blue on most UK maps
There are hundreds of rivers in the uk, the best known is probably the Thames.
Thames
Clyce
There are many rivers in the UK, here are just a few of the larger ones, The River Severn, The Thames, The Mersey, The Tyne, The Clyde, The Trent.