We live in Solihull but still take the motorhome to the NEC shows - I don't think there is an additional charge over and above taking a car if just visiting for the day you just get directed to the perimeters of the car park.
There is normally a temporary caravan club site set up but I would recommend the Caravan club site at Wythall, Birmingham which is about a 20 minute drive along the M42 or the camping and caravan club site at Kingsbury Water park which is about 20 minutes to the North if you want to stay over.
------------- It's only an expensive hobby when it's parked on your Drive....use it, love it , live it.
There is also an independent campsite (if you are not a member of either of the 2 major clubs) which is not very far from the NEC and very popular when the Caravan and Motorhome show is on. Not stayed there myself but have paid a quick visit to the campsite which looks very nice.
We have not stayed at somers wood as it is too close too close to home but we have heard nothing but praise for it . It is adults only (not in the seedy sense) which may be an added benefit,
------------- It's only an expensive hobby when it's parked on your Drive....use it, love it , live it.