Updated /personalisation based on CCM-7937, CCM-7780 and CCM-8133. I also:

- added sentence about no spaces in placeholder text following Mike Houston's comment saying that
we need to be more restrictive as we're generalising across multiple suppliers and template systems
- added anchor links at top of page to help with navigation between the 2 types of personalisation and avoid the custom fields section being missed

Author: emmagifford

docs/assets/personalisationexampledata/personalisation-example-data-nhs-notify.xlsx

@@ -10,14 +10,19 @@ permalink: /using-nhs-notify/personalisation
 section: Writing a message
 ---
 
-You can send personalised messages using a single template.
+You can send personalised messages by adding personalisation fields to a single template.
 
-To personalise a message, use double brackets to add a placeholder to your content. For example:
+Use double brackets to add a placeholder to your content. Do not include spaces in your placeholder text. For example:
 
 {% include components/inset-text.html
-    text='Hello ((firstName)), your NHS Number is ((nhsNumber))'
+    text='Hello ((fullName)), your NHS Number is ((nhsNumber))'
 %}
 
+You can use:
+
+- [Personal Demographics Service (PDS) personalisation fields](#personal-demographics-service-pds-personalisation-fields)<!-- markdownlint-disable-line -->
+- [custom personalisation fields](#custom-personalisation-fields)
+
 ## Personal Demographics Service (PDS) personalisation fields
 
 NHS Notify uses the [Personal Demographics Service (PDS)](https://digital.nhs.uk/services/personal-demographics-service) to find and populate certain personalisation fields for each recipient. This happens automatically when you [tell us who you want to message]({% link pages/using-nhs-notify/tell-us-who-you-want-to-message.md %}) using recipients' NHS numbers.
@@ -26,20 +31,15 @@ You can use the following PDS personalisation fields in your templates:
 
 - fullName
 - firstName
-- middleNames
 - lastName
-- namePrefix
-- nameSuffix
 - nhsNumber
 - date
 
 Any placeholders in your content need to match the PDS personalisation fields.
 
-## Providing your own personalisation data
+## Custom personalisation fields
 
-You can provide your own personalisation data.
-
-Do not send us personalisation data that's already available in PDS. We'll use the PDS data over your own data in this case.
+You can add custom personalisation fields that use your own personalisation data.
 
 ### If you're using NHS Notify API
 
@@ -64,3 +64,56 @@ For example, if you wanted to include 'practice' as a personalisation field, the
 {% include components/inset-text.html
     text='nhsNumber,requestItemRefId,personalisation_practice'
 %}
+
+### Providing example data
+
+The data used in your personalisation fields can affect the formatting and length of your messages. This could make some messages cost more than expected.
+
+You'll need to provide example data if you're using custom personalisation fields. This is so that we can show you what your templates will look like with different lengths of data in your personalisation fields.
+
+Download and complete our [example personalisation data spreadsheet]({% link assets/personalisationexampledata/personalisation-example-data-nhs-notify.xlsx %}).
+
+The placeholders in your content must match the fields in the 'personalisation field' column.
+
+You'll need to provide short, medium and long lengths of example data for each of your personalisation fields.
+
+For example, if you had ((hospital_address_line)) as a personalisation field, you might choose the following example data:
+
+{% include components/inset-text.html
+text='
+
+- Hospital A - short length
+- Hospital ABCDE - medium length
+- Hospital ABCDEFGHIJKLMN - long length'
+  %}
+
+It's up to you to decide how many characters to use for the different lengths.
+
+If your data will be a fixed length for a particular personalisation field, use 3 different examples of the same length.
+
+Your example data does not need to be real data.
+
+### Fields to avoid for custom personalisation
+
+If you want to use custom personalisation, do not use the following personalisation fields:
+
+- emailAddress
+- phoneNumber
+- addressLine1
+- addressLine2
+- addressLine3
+- addressLine4
+- addressLine5
+- addressLine6
+- addressLine7
+- [PDS personalisation fields](#personal-demographics-service-pds-personalisation-fields)
+
+Custom personalisation will not work if you try to add it using these fields. This includes variations such as spaces and upper or lower cases.
+
+You can include extra words in your custom personalisation placeholders to make them different from the fields to avoid.
+
+For example, if you wanted to include GP practice phone number as a custom personalisation field, your placeholder could be:
+
+{% include components/inset-text.html
+    text='((GP_phoneNumber))'
+%}