Well as regards Tupe, I have experienced a TUPE transfer, it worked very well, transferred over final salary scheme applied because it was part of my contract,service years were also transferred, attempts were made to change terms and conditions which were successfully challenged, so all in all it was a success.
It works well when the employer is willing to transfer on those terms (albeit with a bit of negotiation sometimes), if the employer doesn't want to play they either use a loophole or rely on the employee not risking the time, cost and effort of an employment tribunal.
The loopholes are there for the taking, there are numerous employees having to apply for their own job these days, if you are given the choice between signing up to new terms or having to apply for your own job its high risk to do the former unless you are financially very secure.
You only have to look at the Wirral binmen to realize how little weight TUPE holds, every time the waste contract change, the binmen got a new contract which is either less money or different hours.
Unless the new role is 100% identical to the old role in terms of individual and department, then an efficiency or restructuring has taken place and the loophole is open.