@jeremy
Really sorry for you chap. That's a lot of tools and a lot of money to replace them.
There's always going to be some horrible person around that will steal tools. You have to learn from this. You must now insure your tools, It's not that expensive. I add mine on to my PL insurance and it gives me great peace of mind. in addition, you must make sure that the tools are covered in your vehicle over night as some insurance companies offer this as an extra, but do not make it clear when you take out the policy.
In addition, dead locks. Good quality deadlocks. Both my neighbours vans have been broken into and tools stolen. Mine has not been touched (kiss of death!) and I think it is because of the deadlocks. The thieves want quick easy pickings and will go for the easy van, not the hard van. However, if they really want to get in, they will, hence the insurance.
Sorry again chap.