If you want to increase your credit score and improve your credit file, then yes! If you want to get better choice in loan options and loan pricing, then yes!
But please note that StepUp won't be a good fit if you defaulted on a credit agreement in the last 12 months, have an active Country Court Judgement (CCJ) or Individual Voluntary Agreement (IVA), or been declared bankrupt or insolvent. Lenders tend to decline applications if any of these appear on your credit file, irrespective of your credit score.
StepUp won't be a good fit if you are highly indebted, behind in your bills, or subject to debt relief and debt management plans. If you're struggling to make payments on time, you may end up hurting your credit score - which is the exact opposite of StepUp's intent.