Dear Fiona,
As you see the from the number of bids, you can see the easiness of the project. So, I have bidden a less price. I can go less for this, if we your requirement is as per your statement.
I can create you client signup form either in MS-Word or MS-Excel. The client sign up whole data's can be maintained in MS-Excel. In this way, You have to send the form (as a mail attachment) to your client, and get received the fill form. Press the update button, to get update in the database. As an additional feature, I could add the client details, as contact in MS-Outlook.
However, as a professional, I would explain the latest improvements available in the client data collection, and management of the client details. Present improvement says about "online forms". You have to send the link to the client. Once the client press submit the button in the form, your data's are automatically populated in Google Spreadsheet Database, which will be automatically updated in the Google Contacts. Online forms has added advantages.
I leave it to you, which on you want.
If you need any other clarification, we can have a discussion.