What's worse is I think your 3.55% is introductory.
I checked the details of the loan offer and I have seen nothing to indicate it is introductory. As it is an SVR they do reserve the right to raise it, but nothing that it is an introductory offer for a defined period of time
Let me rephrase re the "not benefit from changes in the SVR rate" comment:
When I signed up to BOI, I was on the standard SVR rate - which had some code listed against it (would need to look it up to get the correct detail. I always knew this was their standard SVR. A 80% LTV SVR came out, but as I had not signed up to this I did not quality automatically. I assumed I would have to apply for this to get it. Same applies for the 60% LTV in January of 3.9%. The fact they did not allow me to move was another matter.
With KBC I signed up to their "special" <60% LTV SVR product with a rate of 3.55%. The new product they are selling to new customers is the exact same <60% SVR product; it just has a different price to the existing one. If it had been a new <59% SVR product, it may be a slightly different scenario as you are purchasing something different. But I am now effectively paying a different price for the exact same product.
If the product had been a special "0.95% off" the SVR rate, and the new product was a special "1% off" the SVR rate, again it would be different
I was on to KBC this morning and did relay my disappointment to them about this practice. I told them I had moved to them in good faith, and they have not shown me the same good faith in return. I advised them the only action I have available to me in the short term is to move all my savings accounts from them as they mature. I also advised if any further rate drops are not passed on, I would be closing my credit card account with them also. I know it will make little difference in the grand scheme of things, but at least I am not rewarding their 'poor behaviour' towards me.
I will add that although I am only 2 months into a switch, and obviously would not switch for 0.05%, if the margin gets bigger and a better offer comes onto the market, I will happily consider moving again. I did point out that the customers they have acquired via switching over the last while are those who do not suffer from inertia and are in a position to switch, so may not be the best policy to target these customers if they wish to maintain them.