Question Author
Thankfully, the matter has now been resolved and the solicitor has issued a cheque to my relative to cover the 'Gift'.
Apparently, the credit check was, as dzug2 suggested, for security/identity purposes.
Themas, I think the solicitor was acting in the best interests of the intended recipient, my relative, and I am not aware that such a check would be illegal or indeed unethical, but I;m open to correction. Anyway, thanks once again for you input, everyone.