You dont need to use them to do the foreign exchange part. You can use another company for FX and transfer to your Investec account. The come under the UK guarantee which is been increased I think.
They have online accounts and paper accounts I am told. From What I am told their use of sending user names by email and passwords by text does not sound very secure, and I for one would not trust my savings to such a system. Considering the lengths banks like RABO and NIB go to give you good online security, I will be going with the paper account with Investec if I choose to go ahead with them.