When it came time to replace our downstairs toilet we checked out the "WaterWise" web site for a Product Recommendation. From there we chose the Twyford "Flushwise". This is a dual-flush model using either 4 or 2.6 litres. The price is around the £210 area. We got ours from a local Plumbing Wholesaler and this Twyford range is generally available via the Plumb Centre, City Plumbing, Jewson and PTS in the UK.
There is a wide range of water-saving toilets to choose from. You may wish to try options from Caroma who offer the "Profile5" which uses 3 or 4.5l of water per flush. It is, however, far more expensive. You can also try the "Riviera" by Lecico with a 4 or 2.6 litre flush.
The Twyford Flushwise range of toilets received the "Waterwise Marque" in 2008 & 2009. Ours was fitted by a local plumber with no difficulty. In fact it is easier that the 'regular' toilet as it has no external overflow.
We recommend the Twyford range as it works well at a good price.
At the same time we replaced the downstairs toilet the small sink was replaced too. The suite in this room was a very bright grass-green which may have been very fashionable when it was fitted back in the 1980's but was looking sorely dated by 2009. That and the work of 25 years of lime scale had reduced the effectiveness of the flushing mechanism as well as covering everything in white staining that would not shift.
The sink itself has no special water saving features (albeit - it is tiny!). However the tap does have a flow restrictor. We made the mistake of not really shopping around before going to the plumber's merchants so we ended up asking the counter-staff for their assistance. Since they couldn't offer anything with clever tap mechanisms all they could show us were taps that would allow the fitting of standard flow restrictors. They then asked us which level of restriction we wanted. We just went for the average one based upon their recommendation. However this proved to give too high a flow rate. As the flow-restrictor is a £1 plastic gizmo that sits just inside the tap water exit point then they can be changed. Next time we will get the one offering the MOST amount of restriction, ie, lowest flow rate. Afterall this is only a downstairs toilet and no one will wash their hair here.
Update: August 2010.
Pictured left is the new toilet for the upstairs shower room. The old toilet stopped working so we took the opportunity to replace it with a new one. If this one looks familiar it is for good reason. This is the same make and model as the one shown above. It is a Twyford "Flushwise" from the "Galerie" range. It was shipped to us with a broken cistern lid. After two weeks we finally managed to get the shop to get us a replacement.
When our kitchen was replaced the flow rate to the kitchen sink tap was much reduced for reasons unclear. We found this to be a problem as this sink is used for washing up where it is common to fill a bowl of hot water. With any sort of flow restriction you have to wait a long time for the bowl to fill. From our experience this is the one tap in the house you need no resrictor on.
In the Summer of 2010 we finally got Thames Water to fit our water meter. We lived her for over a year before we realised that we didn't have one. We just naturally assumed we did. Monthly bill went from £80 to £14 overnight. Wish we had noticed sooner!