Nik and all battery's always connect positive first and remove last when removing or charging , this is because you cannot Short the battery with either jump lead or spanner against an earth
When jumping a ranger rover you should put battery to battery only so red/ positive from doña battery onto flat battery red/ positive first then black/ earth reversal is black first then red
Now years ago you would-always put the earth from the doña battery anywhere on flat battery's car earth ie frame or a metal part of engine,this was because it would use the charging system of the doña car the reason you never should put battery to battery is that if the doña battery was duff as well the volts between battery's could level out ie the flat battery could draw the the little power out of the weak doña battery and you could end up with two batterys without enough power at all. But with the delicate electrics in modern cars its a risk using the doña cars system in Case I guess it's causes a surge .
Small pre charged boosters are fine
The booster that should not be used are the type garages have big trolley type that can quick charge a battery, Which in itself is not good for the battery or your car hope this helps
Above good for diesel but petrol should not be connected like that or you could burn something. Petrol should be earthed away from battery on a suitable unpainted earthing point. There should not be a problem using a good quality booster pack or boost charger set to start. If they are connected properly. Think most problems come from connecting petrol models up straight to battery.