Good on them
The politicians can't pin anything on the companies and they know it. All this enquiry bullshit is a pathetic attempt at keeping attention on the corporations so that MP's don't actually have to do some work fixing the tax structure (probably because that would knacker their own tax arrangements.) At least some MP's have the decency to not waste everyone's time.
You want to fix the multinationals tax situation, do any or all of the following:
1 - 1% tax on all transactions where payment is made by a UK entity. A small charge that is the bare minimum cost of doing business in the UK. Adjust existing taxes so that small or national businesses (or anyone who actually already pays 1% or more) see no increase, multinationals can suck it up.
2 - Withholding tax of about 5% which corporations can claim back IF they can prove they have already paid tax on that earnings within another jurisdiction.
3 - Tax money as it is moved out of the UK, BUT make this refundable/not payable IF the company gives written validated confirmation that it is being moved to its final jurisdiction this financial year (i.e. an undertaking that it will not then go to Holland and then on to Bermuda). I can't see this having an effect on anyone who isn't trying to pull a double Irish Dutch whatever.
4 - Payments to sister companies to be heavily restricted to reasonable amounts for goods and services received only, e.g. no more Starbucks UK paying millions in brand licencing to Starbucks US to reduce the profits on their books. This is the one that sails closest to the tax evasion wind in my opinion.