When it comes to crime such as thieving/smuggling there are essentially two forms of enterprise: the individual entrepreneur and the thief/smuggler who knows the product, where to find it and how to obtain it and minimise risk, and how to dispose of it. They are very much like each other except the latter is unlikely to be acting as a solo enterprise and is highly skilled and efficient in the teamwork, from beginning to end, which will successfully accomplish the task.
I do not know what the figures are for recovery of stolen Landies but I suspect they are less than ten percent. And again I have no idea of the figures, but I suspect the organised stealing and disposal of Landies accounts for the majority of thefts. So how many organised gangs do you think we might have in the UK? Are they foreigners? After all the sex-trade and certain drugs are controlled by non UK natives. Is the stolen Landie trade lucrative? Yes. Where's the market destination? What countries are likely to have less than rigid rules about the re-registering of 'imported' cars?
I refuse to believe that the police do not have some of these answers and/or can obtain more intelligence from existing files and reports yet ignore the problem because insurance companies (and ultimately the owners) suffer the consequences and increased premiums.
It's not a crime which causes public outrage (unless an MP loses one) so there is little pressure on the police to make it a target.