UK Postcode validation for Contact Form 7

I need a simple tool (plugin) to check the postcode entered in Contact form 7 (the postcode is a text field in contact form 7).

Background information:
The UK postcode consists of five to seven alphanumeric characters
The first part is called "Outward Code" and the second part "Inward Code"

The outward code is the first half of a postcode (before the space). Some are non-geographic, i.e. does not divulge the location.
The outward code consists of:
- 2-4 characters long
- It always begins with a letter
- It may end with a number or letter

Examples of outward codes include:
L1
W1A
RH1
RH10
SE1P

The inward code is the second half of a postcode (after the space). The inward code assists in the delivery of post within a postal district.
The inward code consists of:
- Exactly 3 characters long
- It always begins with a number

Examples of inward codes:
0NY
7GZ
7HF
8JQ

The tool needs to:
1) Check if the postcode was entered correctly in the UK format according to the rules above.
2) Be configurable, so the website admin will have an interface in WordPress to add / update and delete all outward postcodes that they work at (which are in my case the areas of material collection)
3) Check if the outward part of the postcode is within the list of outward postcodes that were entered into the WordPress CMS that you will develop.

It needs to be compatible with Contact Form 7 text.
Example:
Material collection outward areas as entered in CMS (B1, B2, B8, B16, B21, CV1, CV7, CT1, CT7, CT50, MK1, MK18, NG90)
So, if the postcode field in contact form 7 (text) was entered as "B1 8AC", then the postcode is VALID and should continue the Contact 7 form normal flow, i.e. the submission is accepted and continues normally.
However, if the postcode field in contact form 7 (text) was entered "B3 1AD", then the postcode is INVALID, and a message should be displayed on the screen (message to be configured too, but it may look like "Sorry but we do not collect any material on this area") and the submission is rejected.

Be aware that currently Contact form 7 is integrated with Zoho CRM via a plugin. This tool must not interfere with this configuration/integration.