Don't know a great deal about Durnfords movements prior to Isandlwana. But came across this information from a Mr John Young.
At 2 a.m. on 14th January, Durnford roused his men, and readied them for a forced march at 4 a.m. As Durnford was on the summit of Kranz Kop preparing to descend into the valley leading towards the drift a galloper from Lord Chelmsford met him. The dispatch from Chelmsford was forthright and to the point:
Unless you carry out the instructions I give you, it will be my unpleasant duty to remove you from your command, and to substitute another officer for officer for the commander of No. 2 Column. When a column is acting SEPARATELY in an enemy's country I am quite ready to give its commander every latitude, and would certainly expect him to disobey any orders he might receive from me, if information which he obtained showed that it would be injurious to the interests of the column under his command. Your neglecting to obey my instructions in the present instance has no excuse. You have simply received information in a letter from Bishop Schroeder[sic], which may or may not be true and which you have no means of verifying. If movements ordered are to be delayed because report hints at a chance of an invasion of Natal, it will be impossible for me to carry out my plan of campaign. I trust you will understand this plain speaking and not give me any further occasion to write in a style which is distasteful to me."
The following day Durnford was ordered to the vicinity of Rorke's Drift, with a few companies of his N.N.C., five troops of the N.N.H., and a rocket battery under the command of Brevet Major Francis Broadfoot Russell.
On 19th, Durnford received further orders to relocate the force under his immediate command to the Zulu bank of Rorke's Drift. On the 20th Number 3 Column reached Isandlwana.
On 21st, Lord Chelmsford sent out a two-pronged reconnaissance to ascertain the whereabouts of any Zulu forces. Elements of the reconnaissance came into contact with Zulu forces late in the afternoon. Messages were passed back to Chelmsford at Isandlwana requesting reinforcements.
In the early hours of the morning of Wednesday, 22nd January, 1879, Chelmsford made the decision to divide Number 3 Column, leaving one half at Isandlwana, whilst marching out with the other to meet the Zulu threat.
At 3 a.m., Lieutenant Horace Lockwood Smith-Dorrien, of the 95th (Derbyshire) Regiment of Foot, a special service officer detailed to transport duties, was ordered to return to Rorke's Drift. He carried orders for Durnford, instructing him to reinforce the camp at Isandlwana with the forces at his disposal.
Durnford received the orders at about
7 a.m. Durnford moved on towards Isandlwana with his mounted troops, having given orders for his infantrymen to follow on.
About a quarter of a mile from the camp at Isandlwana, he encountered a fellow Engineer officer moving in the opposite direction, his name was John Rouse Merriott Chard, a lieutenant from 5th (Field) Company. Chard informed Durnford that Zulus had been seen on the hills to the north of the camp. Durnford instructed Chard to inform the two N.N.C. companies to hurry on to Isandlwana.
Shortly after 10 a.m. Durnford arrived in the camp. He had with him some two hundred and fifty N.N.H., 'D' Company, 1st Battalion, 1st Regiment, followed on behind escorting Russell's rocket battery. Bringing up the rear was Captain Walter Stafford and his 'E' Company, 1st/1st N.N.C. acting as the baggage guard.
Source: Brevet Colonel Anthony W. Durnford, Royal Engineers.
Account written by John Young
I'm not sure how far RD is From Isandlwana. But it looks like it took nearly 3 hours for Durmford to get to Isandlwana.