You are in the Republic of Ireland and contemplate a visit to the UK. Importantly, you have recently completed two years in the UK under the Youth Mobility Scheme. This is a well-known pattern with YMS people, more about that later.
Your first option is to take a ferry or flight from the Republic to the UK. We went over this in How long before I can re-enter the UK after Youth Mobility?. Movement within the Common Travel Area is regulated differently and imposes various constraints and restrictions that some find arcane, but they are nonetheless rules. There is nothing more that can be added to this strategy other than what's already pointed out. You can be in the UK legally for 7 days. Some YMS people ignore this restriction and the enforcement side tells us that it's troublesome to detain and remove these people when they finally get caught, and that's why Immigration Officers worry about it and hence 'well-known pattern'.
Your next option is to "channel hop". This involves leaving the Common Travel Area altogether and entering the UK as a fresh arrival. In this case you will have an inspection per the Immigration Act 1971, more commonly known as a "landing interview". Three things can happen as a result of your landing interview...
- You get stamped in for 6 months, this is the most common outcome;
- You get 'temporary admission' for a period which ranges from 24
hours to 15 days (this is a medium bad thing); or
- You get 'bounced', or more formally, 'removed' (this is a catastrophically bad thing)
The final option is to apply for entry clearance from within the ROI. This involves filling out an online form just like you did when you applied for the YMS. If it's approved, you will get 6 months with no hassles at the border. It would also be extraordinary because you're a non-visa national already inside the CTA. I would bet the chances of refusal to be about 98% because you are trying to build up a life in the UK, at least on paper.
Those are your options. All of these have advantages and disadvantages and selecting the 'best one' is something only you can do. The specific rule you are up against is laid out in Appendix V, Paragraph 4.2 (b)...
V 4.2 The applicant must satisfy the decision maker that they are a
genuine visitor. This means that the applicant:
- (b) will not live in the UK for extended periods through frequent or successive visits, or make the UK their main home; and
And to be fair, your narrative fits this rule. It's pretty much what you are trying to do. So as soon as the IO spots your YMS visa and then finds out you have been in the ROI the whole time alarm bells will sound and he will get worried. This will take the form of an aggressive "grilling" that people find unpleasant. And when they find out you have a bf in the UK they will get visibly upset and bring the duty Chief in on the interview. If, and when the duty Chief is brought in, you will need to very, very careful. Some people miss the importance of this part and just continue their rant. The outcome will depend on your personal impact and articulation skills, some people succeed and some do not. We have a modest, but authentic cross-section of removals in the site's archives.
The Youth Mobility Scheme is a Tier 5 visa within the Points-Based System. Tier 2 visa holders have a regulated cooling-off period, but this is for T2 only and does not extend to Tier 5.