It would be brilliant if you could manage to get a picture
Our native spiders do not get anywhere near the size you are suggesting. This spider sounds more like an escaped pet that is thriving off native wildlife. As the exact species is unknown it would be wise to keep a distance.
It might be a good idea to contact your local RSPCA and ask for some advice and assistance. Try looking at this site for RSPCA info:
Stubbington Ark Online