you are correct about HOMEBOND, i saw a housing development that had to change TF suppliers midway because HOMEBOND wouldnt stand over them (eventually premier did, with a bit of remedial works to them).
You are correct about the CE being a mark of suitability of material or manufacture to conform with european directives, however you are incorrect that it superceds the IAB cert. The IAB testing includes issues such as compliance with irish building regs (structure, fire, ventilation, materials and workmanship, energy conservation, disabled access etc etc)which CE does not.
Its perfectly suitable in determining the performance of a material, but not for a prefabricated structure.
You will find that it is incrediably difficult to get an architect / engineer to certify the compliance of prefabricated structures with irish building regs without an IAB (or sometimes BBA) cert. Its up to the supplying companies to prove compliance, which costs a lot of money.