I am just reading Peter Beresford Ellis's book, the Druids, and he details direct linguistic ties between various Celtic languages and Sanskrit or Hindi e.g., Druid ==> Dru (Oak) id (Vid) Hindi for wisdom or knowledge. However, the puzzle is the accent. Is the same true for Irish and Scottish Gaelic?
The other, and perhaps simpler, alternative explanantion is that the Indian individuals in question learned their English in an area where Welsh expatriates had taught English to the local population. If true, there are undoubtedly Indians who speak with a Scottish or Irish "lilt". The influence of local accents can certainly survive 300 or 400 years. For example, in parts of Maine, they speak with a distinctly East Anglian or West Country accent reflecting the geographic origins of 17th Century settlers - the famous comedy duo "Bert and I" have accent reminiscent of Cornish or West Country accents.
If I remember my studies, the Gaelic has two main branches Cymric (welsh and breton), and Scots/Irish. There are quite a few disimilarities between the accents etc. I am not sure about where similarities between Irish Gaelic and Sanskrit may lie.
Since you are reading a book on druids, there has long been speculation that the early Indo Europeans who moved into India were closely related to the Celts. I have read from several sources that linguistically there was some evidence for this. The druid priest caste had many similarities to the Brahmin's priest caste. The functions of these priests in both Celtic and Indian life were somewhat similar. The druids wrote nothing down but the vague hints about their beliefs even echo some Hindu beliefs. Since Wales was a seat of power for the druids there may indeed be a very distant link between the peoples. The more Germanic European culture groups tended to have a shamanistic approach to religion without any evolution of a special caste of priests. I read that same book, that you are now reading, and believe that there is a link.
I can't speak to the matter of accent but presumably if the dialects are similar the accents would be also. Berresford Ellis in his book "The Celts" points to a direct link between Vedic Sanskrit and Old Irish. He writes:
"When scholars seriously began to examine the Indo-European connections...they were amazed at how old Irish and Sanskrit had apparently maintained close links with their Indo-European parent. This applies not only in the field of linguistics but in law and social custom, in mythology, in folk custom and in traditional musical form."
To illustrate similarities in language of the Vedic Laws of Manu and that of Irish legal texts, the Laws of the Fenechus aka the Brehon Laws, he cites (the first in Sansrit, the second in Old Irish): arya (freeman), aire (noble); naib (good), noeib (holy); badhira (deaf), bodhar (deaf); minda (physical defect), menda (a stammerer); names (respect), nemed (respect/privilege); raja (king), ri (king); vid (knowledge), uid (knowledge), etc.
Here's a clue to the ancient location of the Indo-Europeans. Danu, sometimes anu in old Irish and Don in Welsh (also surviving with the Continental Celts) was the 'divine waters' which gushed to the earth in the time of primal chaos and nurtured Bile the sacred oak, from whom the gods and goddesses sprang. Her waters formed the course of the Danuvius (Danube). Of course there's the pesky problem of the River Don in Russa: which was named first? There's also a Don River in Scotland and probably elsewhere too, derived from the original root name.