Let alone the UK - in South Africa hundreds sitting for Itikhaaf has become the fashion.
Itikhaaf is Sunnat-e-Muakkidah ala Kifiyaah - meaning that if one person sits in Itikhaaf then the whole locality is absolved of the duty and responsibility.
I have been researching how many Sahabah sat with Nabi (S.A.W) and how many re-sat when he told them to re-sit. So far I cannot find. Moreover, in his order of re-sitting, Nabi (S.A.W) did not instruct others to sit.
Furthermore, I cannot trace if:
1) The Khulafaa-e-Rashideen sat and how many sat with them;
2) The prominent Sahabah (R.A) sat and how many sat with them;
3) The Fuqahaa (A.R) sat and how many sat with them;
4) The Mutakalneen (A.R) sat and how many sat with them;
5) The Muhadditheen (A.R) sat and how many sat with them;
6) The Mufasireen (A.R) sat and how many sat with them;
7) The Ahle Tasawwuf (A.R) sat and how many sat with them;
Note that the speech, inspiration, dream, and actions of the pious personalities are not a proof in Shariat. (see full article on site).
The food and time wastage in huge Itikhaafs is astronomical.
The introduction of Bidaat has increased in such Itikhaafs.
Let alone going out in Jamaat, it is better to stay at home, turn to Allaah, become regular in Salaat with Jamaat, make Tilawat of Qur'aan, Zikr, fulfill the rights of man, be generous, fulfill the Fardh, Waajib, Sunnat, make Du'aa, and win the Mercy of Allaah.
If the person has the option whether to sit for Itikhaaf or go out in the path of Allaah, then definitely one should go out in the path of Allaah.
May Allaah guide us all.