I am going to be straightforward in here. I am currently doing PhD at university in UK within the field of power electronics. However my previous background was related to general Energy Engineering (i had some modules in electrical engineering, however majority was related to thermodynamics, heat transfer, some chemistry, fuels, combustion), thus I had a lot problems in adjusting to the topic (systems modelling, Matlab Simulink, signal processing) and I am still not feeling confident in this field. But straight after graduation I did not have many options and one of my module leaders told me about available PhD position at the same university, where I did my master. I started by the end of November 2017. I participated in a few, very professional progress meetings and all the time I felt lack of confidence in power electronics' field. Thus it was full (extremely) of stress. Since then relations with my supervisor become very cold, however I got some friendships with my office colleagues (but I have a lot of problems talking about my research project being aware that I can easily make a mistake and say sth stupid). Suddenly (like 3 months) ago I noticed Graduate Scheme job offer in the building close to department and I made an application. It's not a typical job as the 'company' is on the campus and project is research-based but with normal salary. I was rejected after assessment day, but suddenly (yesterday) i got an offer. They asked me whether I am still interested, I said yes - waiting for formal contract etc.
I am aware that many people regret decision about withdrawing from their PhDs as it become difficult to come back. But this job is not a typical office one, it's in the lab with manufacturing, processing etc. and even description said that can lead to PhD. What would you do? I am ware that some tough decision will be in front of me - asking university to withdraw me from PhD program, but I know that I will not get better offer than this, maybe ever. Other question - how long time before I have to inform university about withdrawal?