Unfortunately, HM Revenue and Customs rules require shares within an Individual Savings Account (ISA) wrapper to be held in a stock broker nominee account. As a result, personal CREST accounts cannot be used for ISA shareholdings.
This is probably the biggest drawback of CREST membership, since choosing the advantages of a CREST member means giving up the tax advantages of the ISA. However, it is of course possible to open a nominee account for your ISA investments and use a CREST account for those kept outside an ISA.
CREST personal membership is possible with a Self-Invested Personal Pension (SIPP), if the SIPP provider permits it. Since a SIPP is a trust account, the CREST membership will be in the name of the SIPP trustees rather than you as an individual.