My First Rose

I recently bought my first ever rose, a bare root Harkness rose, "Celebrating Life".
I have kept it in the polythene bag it came in, with the top slightly open and have kept the roots moist and have kept it in a cool place.
Until now, the weather here was cold and wet. As the last couple of days here have been dry and sunny, although it is dry but overcast today, the soil should be dry enough to plant in without compacting around the roots.
My question is - I will be planting my rose in my front garden which is South facing. The soil is freely draining sandy loam and is slightly acidic (a ph test using the TestWest soil testing kit I have resulted in a light yellow liquid after the contents of the tube settled).
When I plant my rose, should I dig some mpc (Westland), or peat (Westland Irish Moss Peat), or a bit of both into the soil in the planting hole ?
I don't have any fertilizer of any kind at the moment, but everything in the garden is thriving so I'm guessing that the soil nutrition is good.
Plants currently in my front garden and thriving are - Cherry laurel; lots of new growth and is just starting to flower. Photinia "Red Robin"; lots of new young red leaves starting to appear. Buddleia davidii; lots of new shoots forming. Pieris "Forest Flame"; flowering profusely and now beginning to produce new, red, young leaves. Holly; producing new young leaves (flowers later in the summer). Eucalyptus gunnii; now covered with flower buds. Forsythia; fully in flower. Day lily; currently putting up new shoots. As these mature plants are thriving year after year in my front garden, do I really need to add any fertilizer or other products when planting my rose ?
Thanks in advance

 

Thank you @wiseowl
I bought it to plant in memory of my Mum so it will be an only rose (for now...I may add another one or two at a later date ).
I understand that you are our resident rose expert. Will the soil type (slightly acidic sandy loam) in my front garden be ok as it is, or should I dig in some mpc, or peat, or a bit of both into the planting hole ?

 

Thank you

 

I'll post photos later once I've planted it. I just need to nip up to the shop for a couple of things, so will get my rose planted as soon as I'm back. It's sitting in water at the moment but will be in the ground within the next hour or so