Wild Isles

Four-spotted chaser

Four-spotted chaser

Somerset Levels, UK

The part of the sequence featuring the four-spotted chasers was filmed on a reed bed in the Somerset Levels [1].
[Link 1]

Emperor dragonfly

Anax imperator

Langford Lakes Nature Reserve, Wiltshire, UK

The part of the sequence showcasing the hobbies hunting dragonflies was filmed in Langford Lakes in Wiltshire by cameraman Simon King, as per local reporting [1]. Though several dragonfly species are shown, including a four-spotted chaser (at 1:16 and 1:21) and various hawker dragonflies, the largest focus is placed on the female emperor dragonfly (based on british-dragonflies.org.uk [2]) laying its eggs on the water's surface.
[Link 1] [Link 2]

Eurasian hobby

Falco subbuteo subbuteo

Langford Lakes Nature Reserve, Wiltshire, UK

Atlantic salmon

Salmo salar

River Ness, UK

Common bottlenose dolphin

Tursiops truncatus truncatus

River Ness, UK

Eurasian beaver

Castor fiber

Bamff Wildland, Perthshire, UK

According to local news coverage, the filmmakers came to Bamff to spend 10 days filming the three families of European beavers in the summer of 2021 [1].
[Link 1]

Osprey

Pandion haliaetus haliaetus

Raft spider

Dolomedes fimbriatus

Dorset, UK

D. fimbriatus is often confused for the very similar D. plantarius. Appearance and size are not foolproof means of identifying the species - as with many spiders, only close examination of their sex organs can help us do this with certainty. According to Fen Raft Spider Conservation's website [1]: "Adult males of the two species can be definitively separated by the structure of the tibial apophysis, one of the sclerotised projections on the pedipalps. In D. plantarius it is a bifid structure with a relatively flattened top (mitten-shaped) but it is simpler and more pointed in D. fimbriatus." Further diagrams can be found on Araneae - Spiders of Europe's website for D. fimbriatus [2] and D. plantarius [3]. At 18:57, we get our best look at the male spider's pedipalp. It's clear that the tibial apophysis is markedly pointed, and the blunt mitten shaped structure is absent, so I'm fairly certain this is D. fimbriatus.
[Link 1] [Link 2] [Link 3]

Pondskater sp.

Dorset, UK

Diving beetle sp.

Dorset, UK

Daubenton's bat

Myotis daubentonii

North York Moors, UK

Natterer's bat

Myotis nattereri

North York Moors, UK

It was really difficult to identify a specific Natterer's bat here since, from afar, it's hard to distinguish them from the Daubenton's bat based on ear shape or other, more obvious characteristics. Instead, I relied on an ID document from Nottingham Bat Group [1], which states that in the Natterer's, the calcar, the border of the membrane running between the hind leg and the tail "is S shaped and reaches halfway to the tail." whereas in the Daubenton's the figure of the calcar shows a straighter calcar. It's not much to go on but the individual shown at 24:44 has a distinctly S-shaped calcar, so I assume this is a Natterer's.
[Link 1]

Brown long-eared bat

Plecotus auritus

North York Moors, UK

Common toad

Bufo bufo

Winscombe, Somerset, UK

The behind-the-scenes article [1] states: "So with both the Warminster (in Wiltshire) and Winscombe (in Somerset) toad patrol on speed-dial, we were ready", while this episode's media pack [2] puts the filming location of this sequence as Somerset and Dartmoor. The latter is where the toadlets and leeches drama was filmed, so I assume the former refers to the scenes with the adult toads facing the dangers of cars on the road.
[Link 1] [Link 2]

Common toad

Bufo bufo

Dartmoor, UK

Horse leech

Haemopis sanguisuga

Dartmoor, UK

The predatory leech species featured in this sequence is a horse leech according to the behind-the-scenes article on the programme website [1].
[Link 1]

Green drake mayfly

Ephemera danica

River Avon, UK

Eurasian water shrew

Neomys fodiens fodiens

Dragonfly sp.

Red deer

Cervus elaphus elaphus

RSPB Minsmere, Suffolk, UK

This was filmed at RSPB Minsmere, according to an article featuring producer Chris Howard on the East Anglia Daily Times [1]: "the crew waited about two weeks to capture the perfect light at Minsmere to show the red deer trails through the reedbeds, said Chris."
[Link 1]

Great crested grebe

Podiceps cristatus cristatus