Insurance companies - have you looked at the firms actually providing the services? A lot of commercial contracts have firms in low tax areas as being the ultimate beneficiary / provider. Check them out.
There are many services related businesses that operate in similar ways, where you have a contract in place, agreeing to pay some recipient in an offshore location.
I dont really see much difference between the tech firms, and services firms, due to the exportability of the contractual entity. And many of the tech firms are only shells, which can be involved in the sale of goods as well; look at Ebay.
No, no me the issue is broadening the tax base. Transfer pricing agreements are all good and well, but these are often negotiated. The ultimate outcome seems to be simply what HMRC or whoever can extract after discussions.
If we make things too difficult, these firms will simply go elsewhere, and the goods will be more expensive for the final consumer, because the opportunity to run as efficient a business as possible, including tax efficiency, will have been destroyed.
This may not be popular, but corporate tax is an inefficient mechanism. I'm surprised it's even used any more, and frankly is an unfair mechanism that only hammers the low-hanging fruit of firms who cannot afford the best accountants. Far better to have some broad-based VAT / consumption tax; everyone has to eat and have a roof over their heads, and no matter how good your accountant is, you still need to buy food and keep yourself+family somewhere.