Nordtvedt sees I2a2b-Isles as hitting the British shores around 6,000 years ago. There were other 'early I clades' too such as [the earliest] the Iberia-founded M26 I2a1, I2* and I2b1a-English.
According to Nordtvedt, I2a2b-Isles was founded in northern Germany. Perhaps it got there via LBK bands. From northern Germany, where the snp L161 was 'born', I2a2b-Isles was probably carried to Britain and Ireland via successive waves of people- pre-Celts, Celts and later Anglo-Saxons. Owen has conjectured that the Anglo-Saxons account for at least some of the I2a2b distribution in England and lowland Scotland. Apparently, Bryan Sykes is in agreement. One can envisage I2a2b carried across by Germanics in small quantities alongside I1, I2b1 and R1a1 in the historical period.
There are currently 8 subclades of I2a2b-Isles- A1, A2, B1, B2, C1, C2, D1, D2. There is a decent [for a small clade] distribution across the north European plain with examples of subclades A, C, and D as well as the oldest B subclade represented on the continent. Germany has most members.
The bulk of I2a2b-Isles is in Ireland. Here, Tim Owen has conjectured, there may be a link to the Cruthin- allegedly Ireland's earliest post-LGM inhabitants. Owen draws attention to a hotspot for subclades C and D around Rathcroghan in County Roscommon, which was once a Cruthin satellite settlement [see 'Genes of the Cruthin'], the bulk of Cruthin settlement being in Ulster.
In Ireland, the subclades appear to be concentrated in the western half of the island, in what are argubly 'refuge' areas. The distribution is spread thinly across the population. The suggestion here is of a relic, pre-Gaelic population, subsumed beneath an R1b-majority Gaelic one.
More research needs to be conducted on I2a2b. It is clearly north-west European and absent in eastern Europe. The branchlines between it and I2a2a separated some 13,000 years ago. Eventually, I hope, the databases will enlarge so that we are able to say more about this fascinating little clade.