Not sure of the data's source (i.e. whether it's based on UKMO or not) but you'll find forecast ascents (tephis) at
http://weather.scorer.homelinux.org/RASPviewer.html as well as a host of other stuff that some of us use.
For those pilots who demand more accurate forecasts can I suggest that you move to somewhere which has predictable weather that isn't influenced by, among other things:
The fact that were an island with much localised weather
We're off the coast of a large land mass
We're on the edge of a sizeable mass of ocean
There's the potential for airmasses to come from the polar, tropical and maritime regions
That the UK is several hundred miles long and you expect a forecast to be accurate for a 20Nm area when weather fronts extend several thousand miles
So, if you want accurate forecasts, move to Nevada (it'll be hot and dry).
If you'd like reliable, consistently accurate weather forecasts in the UK then you're out of luck. The only accurate forecast is an aftercast and, even then, some of the forecasters will disagree about why the weather did what it did!
Forecasters are great at pulling together all the pieces of data they have about what's happening now and what's happened in the past and providing an assessment of what 'could' happen. Sometimes they can be 100% confident of their prediction (Winter in the UK tends to be cold for example and if there's a satpic show a solid layer of CuNims rolling in on a front then it's pretty much like that it's going to be wet). Most of the time though it's a best guess. If you think that you ca do it better then go ahead. If you develop a model that works better than the existing ones then you'll be very rich. It'll probably be good for choosing stock market movements too!
Final point - treat forecasts as a general guide (e.g. wet, low cloud and a NW'ly wind) and be mindful that, like any other FORECAST, it may OR MAY NOT be right. Use your own judgement!