A B757 FLT CREW BECOMES DISORIENTED ON AN INST APCH INTO SAV.

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WE WERE DSNDING FOR LNDG UNDER THE CTL OF ATC. HE HAD CLRED US DOWN TO 2000 MSL FOR WHAT WE THOUGHT WOULD BE A VECTOR TO INTERCEPT THE ILS FINAL APCH COURSE. WE WERE BELOW THE TRANSITION ALT FROM THE VOR TO THE BEGINNING OF THE PUBLISHED APCH. SUDDENLY; THE CTLR CLRED US FOR THE APCH. IN MY HASTE TO 'COMMENCE THE APCH;' I MISTOOK THE HOLD FOR THE MISSED APCH AS THE COURSE REVERSAL FOR THIS ILS. THE CAPT SAID NO; IT WAS THE MISSED APCH HOLD. WE HAD INTERMITTENT GND CONTACT AND COULD SEE THE ARPT AT TIMES. WE FLEW A DOWNWIND AND TURNED OURSELVES ONTO AN INTERCEPT FOR THE ILS. WE CAPTURED THE LOC AND GS AND LANDED WITHOUT INCIDENT. MY BIGGEST CONCERN IS THAT WE WERE FLYING AROUND 'ON OUR OWN' BELOW THE 2600 FT MSA AND THE 25000 FT TRANSITION ALT. WHEN THE CTLR CLRED US TO 2000 FT MSL; WE EXPECTED TO BE VECTORED ONTO THE APCH. CONTRIBUTING FACTORS: OVER 8 HRS OF NIGHT FLT; INCLUDING A NORTH ATLANTIC XING AND MY LOW TIME IN THE AIRPLANE AND LACK OF EXPERIENCE WITH THE FMS. I HAD BRIEFED THE APCH; BUT FEEL THE CTLR ABANDONED US ON THIS APCH.