Here are two UK postcode database available.
1. Full UK postcode database with more than 1.62 million records.
Example
+----+----------+-----------+-----------+
| ID | ZIPCode | Latitude | Longitude |
+----+----------+-----------+-----------+
| 1 | AB10 1GY | 57.147600 | -2.097500 |
| 2 | AB10 1NP | 57.146700 | -2.107400 |
| 3 | AB10 1RQ | 57.146700 | -2.110700 |
| 4 | AB10 1TT | 57.143100 | -2.114000 |
| 6 | AB10 6AA | 57.135000 | -2.115600 |
+----+----------+-----------+-----------+
Price: £19.99
2. Simplified UK postcode database with about 10,000 records. It can reduce server loads while providing enough accuracy.
Example
+-------+----------+-----------+-----------+
| ID | postcode | Latitude | Longitude |
+-------+----------+-----------+-----------+
| 10544 | AB101 | 57.145607 | -2.107954 |
| 10545 | AB106 | 57.136188 | -2.121770 |
| 10546 | AB107 | 57.124924 | -2.132753 |
| 10547 | AB115 | 57.144965 | -2.089854 |
| 10548 | AB116 | 57.141513 | -2.105484 |
+-------+----------+-----------+-----------+
Price: £9.99
After buy and pay it via Paypal, an email will be sent to you with link to download. | 
