For that kind of money we could easily finance the 24/7 machine gun towers I advocate peppered around the coastline of the UK and which could be manned, say, by retired SAS, Marines, Paras etc.
The hitherto impotent immigration authorities could be assigned offices at all our major ports, particularly Dover, for example, where on the spot decisions can be made and the unsuccessful apprehended applicants immediately sent back.
Simple, really. Save all this hassle, wouldn't it?