ขอถามเรื่องวีซ่าอังกฤษค่ะ

Check your university website to see whether there's an English course on offer that you can do and apply to study 3-4 months before the start of your undergraduate degree course. If there is one you can take it as a presessional course and that way you may probably get, if you are lucky, a Tier 4 visa to cover for the duration of stay of both English and degree courses.

You can still apply for a short Tier 4 visa for studying English only, but the sponsor must be a highly trusted sponsor. Then you have to apply for a visa extension in the UK, before that initial visa expires, for your main course of study.  You can only apply for one type of visa only.

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/370866/T4_Guidance_11-14.pdf
read from page 62 of 87 para. 334

It is summer season in the UK during the months of June to September, there may not be courses available for you to take and to stay in the UK to start your degree course without having to leave the country to apply for a new student visa.  

So, if there is nothing you can do then you have to take it the way it is, that is to enter the UK only a month ahead of time.

If you want to know anything about anything you will have to read the full Tier 4 policy guidance.

Good luck and a very happy New Year to you.