What youre experiencing is not unusual when changing from one machine to another. All machines have their little quirks and peculiarities which must be learnt from scratch, just as you did when you first got the Sunbeam. At least now though, youre much better informed and experienced as to what goes into making a great coffee. 8-)
Most likely and so long as your beans are freshly roasted, the problems are due to Dose/Distribution technique. It is also possible (maybe?) that the new machines brew pressure is set too high which is quite common with Domestic Gaggias and others. Anyway, disregarding that possibility for now, set the Double Basket into the PF with the grinder on a slightly coarse setting (around the texture of table salt) and grind enough coffee to fill the basket to a slight rounded heap above the basket rim, tap the PF on the bench a couple of times to settle this initial dose down a bit, add more coffee to achieve the slightly rounded heap above the rim again, tap once, level off with the back of a knife blade or which ever implement/finger you normally use and then Tamp down firmly with a force between 7.5-15Kgs.... the actual force isnt important so long as you use the same force +/- 1.0Kg each and every time.
Try pulling shots using this method and only adjust the grind setting, nothing else, finer if the shots are blonding too quickly or coarser if the shot stream(s) are weak and dark. Its always better to start out with a slightly coarse grind setting and then work it finer until youre getting the 30/60ml Single/Double in 25-30 seconds; always bearing in mind that these numbers are a guide only and that what you need to do to control the shot is observe when the shot starts to go blond and/or watery and stop it immediately. Once you get a feeling for how your new machine performs, you should be able to stop the shots before blonding actually starts and still obtain the requisite volume of espresso within the ideal time period.
Hope this helps a bit Kirsty.... Just change one thing at a time and observe what effect each change has on the resulting brew and then make an adjustment as required. All the best, :)