Hi, it's good that you're doing your research
before you get your beardie.
It's hard for anyone to tell you what wattage basking bulb you will need because it also depends on the room temp, the height of the basking log or rock you will be using and how tall your tank is, etc. You could certainly start out by using a 60 watt household light bulb and see what the basking and cool side temps are with that. Then adjust the wattage accordingly. You have to make sure that you are using either a temperature gun or a digital thermometer that has a long wire & probe on the end as those are the only 2 ways to get accurate readings. If you're getting a baby, they tend to like it warmer so a basking temp of over 100 and up to 110 is recommended. The cool side should be 75 to 85 but no higher with a temp of 80 being ideal.
I think you mentioned that you live in the UK so this link is the best fluorescent UVB that you can get there and even superior to the Rept-Sun 10.0 fluorescent that is available in the U.S.
http://www.valuevivariums.co.uk/arcadia-reptile-lamp-p-2984.html A Repti-Glo 5.0 fluorescent doesn't produce enough UV to be beneficial to a beardie so it would really be a waste of money for you as it didn't rate very good on the UVB testing that was done. There have been some problems with the Repti-
Glo 10.0 fluorescent causing eye problems and other health issues, so I would avoid getting one of those too. Also, please make sure you stay away from ALL compact & coil UVB's as they are VERY dangerous and some beardies have died when being under those bulbs.
If you have anymore questions, please let us know.