I can only assume you have something with very large petrol engines or the QE2! To transport a 35-40ft boat from Scotland to South coast is circa £1200 + VAT +marina lifting/launching fees. This is about 400 miles so 100 miles a bit less but only marginally.
Depends on the size of your boat, I moved ny 28ft Sealine from Portsmouth to Chiswick £250, very reasonavle by road, much cheaper than by sea, which as you would have cost a lot of money. Lots of silly comments from some others, hope this is of use.