Your extraction had enough of a dwell time (delay at the start) but turned into a gusher at the end. This could either be because you are using too little coffee or because the coffee is too fresh. Try filling your basket a bit more.

If the temperature is too low, hitting the steam switch for a few seconds before you start, and turning it off once the coffee starts flowing, will do the trick. (Turning on the steam switch -- not the knob-- switches the machine to the hotter thermostat and forces the heat on).

Other than that, the cure for too sour is to make a more ristretto shot, one that dribbles at the start, takes longer to flow, results in a lower weight shot. You can achieve this either by grinding finer, dosing higher or both. Since you had a gusher and need to dose higher anyway, add more coffee at the same grind.

Your best bet is to go too far in that direction, so your espresso will taste bitter instead of sour. Once you've overshot like this, you'll be able to start interpolating, and find the spot where the balance is right.

You cannot accurately measure the temperature with a styrofoam cup; although it makes for an amusing game. Hitting the steam switch forces the heater to run. The earlier before the shot you hit it, and the longer you leave it on going into the shot, the hotter your coffee will be. Eventually it will stop tasting sour, and taste burnt instead.

You can dose higher by rapping the basket or PF to settle the grinds and adding more coffee before leveling off. This is mickey mouse compared to weighing; but it will rasie the dose. Your first goal is not to get a good shot, but to get a too bitter shot. Once you have that, you know where too sour is, and where too bitter is. If you don't have both, there's no way of finding just right.

In general, beginners tend to make their corrections in too small steps (all the while suspecting the coffee, grinder and machine of undermining them); so it can take them much longer than necessary to tune the shots. Tuning goes faster if you make an overly big change and overshoot the mark, because you then can split the difference. Big changes also give you a clearer idea of the full range of tastes you can get out of a coffee.

It's sometimes best to initially ignore all the espresso making golden rules and remember you have a lot of extraction choices. You can use a 12 gram doses to make a 2 ounce shot in 18 seconds, use a 21 gram dose to make a 1 ounce shot in 45 seconds, or do anything in between. You will not know where the best shot lies unless you are willing to explore these extremes and get an idea of the range of available tastes. I have gotten the best possible shots at both extremes, especially when using non-commercial gear or oddball coffees. Once your technique, gear and coffee are right, you will probably be drawn towards a golden mean in coffee, dose and shot time choices; but until then, it's best to experience the full range.

It could be the coffee you're using.

Hasbean has great coffee but only if you're looking for something bright, acidic and challenging. They don't tend to roast chocolate bomb comfort food type espresso. If you're used to something more in line with Italian espresso, you may need to look elsewhere for your fresh roasted beans.

TooMuchCoffee is a UK based coffee site. Check it out to find recommendations for UK and European based roasters that are more in line with the tastes you may be looking for.

Jon