Cheers for the advice and your right edindave I should put some effort in however had no clue how to pace myself being that there is no one to pace with or no idea what the distance would feel like. In truth it felt like I could do another 30 no problem with another lucozade.
I agree though Gloverfan and feel the same as you. I am faster 20 miles in the ride than when started and find I do not really warm up till then.
Pacing-wise, the general advice is not to ride faster than 'conversation pace' for the first 30 minutes or so - something to do with what source of energy your muscles are using. I'd add in: don't grind at any point of the ride - keep the legs spinning - but especially in the early part.
Training-wise, unless you want a particularly structured approach (about which subject I'm no good), just mix up the rides - shorter higher intensity ones, some, but not too many, endurance rides. Many experts go on about the benefits of interval training - but if you live in a hilly area, they'll sort of give you interval training anyway.
Set yourself some targets - they'll help you focus. I've got two - one for my short loop (22 miles) and one for 100 miles - as they make me cycle in different ways, and keep it interesting. Using a cycle computer I've found it useful to aim for an average target speed through the ride (I go for 20mph, whatever the distance), so if I've climbed a hill at 13mph, I'm going to have to cycle the same length of time at 27mph down the other side. It's crude (and obviously I don't always/often hit my target), but is quite a good way to push yourself.
If you're a club sort of person, 18mph (I gather) will mean you'd fit in fine. I'm not - I really just enjoy pushing myself on long solo rides, and with a fairly unscientific & unstructured approach (no more than 'get out and ride as much as possible on a variety of routes') have seen quite a pleasing increase in stamina & speed in just 6 months or so. But now I'm pushing at my physical limits, so know that the progress will be more marginal.
Just my experience though - people's physiology and fitness will vary enormously, so will all experience different results. The main thing is to have fun doing whatever you do.