There was a number of Manchester Reservists who arrived "late" in South Africa and it is most likely that they would have been assigned to other units. Therefore on arrival in South Africa your grandfather was probably assigned, along with several other men from the Manchester Regiment, to General Sir Redvers Buller’s command and most likely joined the Ladysmith relief column at Frere or Chievely in late December 1899 or early 1900, where troops had been gathering since the debacle at Colenso.
In January 1900 Gen Buller decided to try to relieve Ladysmith by way of Potgeiter’s Drift to the west and set off on 10 January with one mounted brigade, five infantry brigades, eight batteries, ten naval guns and 650 transport wagons – a column 17 miles long. In between Buller and Ladysmith lay the Tugela River and the dominating heights of Spion Kop and Vaal Kranz which were held by 7,000 Boers who were preparing to halt Buller’s advance once again.
A bridgehead over the river was seized on 16 January and the crossing continued unopposed. Lt Gen Warren prepared for a frontal attack against the heights but for one week the offensive faltered and so on the 22nd Gen Buller ordered Warren to withdraw or take Spion Kop immediately. Thus at 23h00 on 23 January 1900 the steep climb up Spion Kop began but, as the sun rose the following day, the summit had still not been reached and the attacking force came under intense fire. The battle raged all day and the accurate fire of the Boers, together with the incompetence of Gen Warren, ensured that the British suffered a heavy defeat with 1,000 casualties (including 300 dead). Gen Buller then personally organised the withdrawal of the entire force back across the river and, though a further advance under General Lyttleton was attempted in early February, Boer resistance again proved too strong. Thus by 10 February the entire Ladysmith Relief Force was back at Chievely, whence it had set out a month before.
Gen Buller, fearing that the defenders of Ladysmith could not hold out much longer, determined to try again in the Colenso area which offered the shortest route to Ladysmith but Botha had mustered some 5,000-6,000 Boers to confront him. On 17 February the advance began again and by the 19th the Boers had fled to the North of the Tugela River. However Gen Buller was slow to pursue the Boers, who were able to regroup around the Colenso kopjes. Not until the Boers were driven from these hills could Gen Buller break through to the beleaguered town.
Into this confined area the British advanced and on 22 February the main attack up the steep slopes began. The fighting lasted several days and casualties were heavy but finally on 27 February, the hills from Pieter’s Hill to Colenso were in Buller’s hands. The Boer army was now demoralised and in disarray and its organisation disintegrated as the Boer horsemen, wagons and guns streamed to the rear in retreat, taking with them the Boer forces which had been besieging Ladysmith. Thus at last the forward columns were able to move into Ladysmith and on 3 March 1900 Gen Buller made the formal entry into Ladysmith at the head of his troops. Thus your grandfather was probably able to re-join his comrades in the 1st Battalion Manchester Regiment, some three months after landing in South Africa.
I very much doubt that you will be able to determine his exact movements but I hope this helps.
Bob B