I’m going to give you your first reply on this – I have no doubt however- that there are people very much better furnished with the details and knowledge than I, that will contribute before too long also. We need a Hugh Warwick input here…….
Hedgehogs are protected under the Wildlife and Countryside Act 1981 – which probably doesnt go far enough for these poor creatures really – but it does restrict the capture, captive breeding and any rerelease of them under the circumstances you describe above.
In summary – it would be considered illegal and would get you into trouble.
Added to this – there is also more recent guidance provided by BHPS on suitable habitat for hogs – and it advises to avoid habitat where there is no evidence of hogs already as there is usually a good reason for it (predators, disease and or food source restrictions). If a habitat were suitable for hogs, they would already be there to some extent.
Having said all the above – you may have identified an option that a respected hog expert could survey and confirm or not whether you could be a potential release site for local hog hospitals who cannot return their hogs to the locations they originated from (for whatever reason). Which could then also provide a monitoring opportunity on a developing hog community.