Each ETF is potentially listed in a different market - ie the DAX tracking ETFs are listed on Xetra and the Swiss exchange while the FTSE tracking ETF is listed on the FTSE. OP would need to check the exchanges the specifc ETF he wants is listed on, and give the Sedol or ISIN to the broker.
However, I am not sure that these ETFs settle via CREST so the issue of a CREST account may be mute. Also, I can understand why a broker may not wish to go through the regulatory and annual costs of registering on a particular exchange if the volume of potential business doesn't justify it.