This freebie is available from almost every single water supplier in the UK and Scotland and not just Wessex Water. You can find a complete list courtesy of Hot UK Deals here. I will focus on the freebies you can get from Wessex Water, but they are different at each supplier.
The free water saving pack from Wessex Water comes with a variety of different items to choose from. Simply select the items you want from the list on the website, complete the form and you should get your pack within around 28 days.
You can also get more information on how to fit the various free devices by following their video guides. You are only allowed one pack per household and they are all quite brilliant. Items to choose from include the ShowerSave, Save-A-Flush, Four Minute Timer and the Tap Inserts Twin Pack.
Thanks to avfcniall at HUKD!