在英国大学的录取通知书中，有几种不同的类型，其中包括Conditional Offer和Unconditional Offer。Conditional Offer意味着学生需要满足一些条件才能被正式录取，而Unconditional Offer则表明学生已经完全符合学校的所有要求，已经被正式录取。

对于应届大四学生来说，他们可能还没有获得毕业证书或成绩单，因此他们通常会收到Conditional Offer。这类offer是基于学校对申请材料的初步审查，并且认为该生有潜力完成学业。为了获得无条件的录取， Conditional offer持有者必须在指定时间内提交达标的成绩和其他可能要求的一些文件。

另一方面，Unconditional Offer则是最理想的情况，因为它意味着学校已经确认了你的资格，并且你可以立即开始准备成为一名正式学生。你需要仔细阅读Offer中的详细信息，并在规定时间内确认接受并支付第一笔学费，以便于获取CAS（Confirmation of Acceptance for Studies），这是一个电子记录，是申请英国留学签证所必需的一个重要文件。

除了上述两种类型，还有一种特殊情况，即Integrated offers with unconditional Pre-sessionals，这是一种为那些语言能力不够但仍然符合其他入学标准的人提供的特别机会。在这种情况下，学生首先参加英语预科课程，然后根据课程结束后的评估结果决定是否继续学习。

CAS itself is a crucial document that confirms your acceptance to study in the UK. It contains essential information such as your personal details, academic background, and course-specific electronic codes. This document is required for visa application and ensures that you have a genuine purpose for studying in the UK.

To obtain CAS, you need to follow these steps: first fill out an Acceptance Form and sign it; secondly, pay the initial tuition fee payment (payment methods include international bank transfer, draft cheque or credit card). After submitting all necessary application materials, it's time to wait patiently – the waiting period can be quite long due to varying numbers of applicants and different levels of strictness among universities.

Here are some general guidelines on how quickly each university typically releases their offers: those that usually take less than one week include Loughborough University, Sussex University, Leicester University Swansea University Aberdeen University Coventry University Bath Spa University Northumbria Newcastle Upon Tyne. On the other hand universities like Lancaster Uni Leeds Uni East Anglia Uni Bristol Uni Sheffield Univ Edinburgh Uni Kent Univeristy Glasgow U Manchester U Reading U London South Bank U Essex Uni Strathclyde & Bangor U Birmingham City may take more time while some universities known for being slow at issuing offers include Lancaster Leeds East Anglia Bristol Sheffield Edinburgh Newcastle Cardiff York Manchester Exeter Liverpool while those known for rejecting many applications include Sheffield Soton Leeds Birmingham Bristol Glasgow Lancaster E Anglia Ncle Cardiff York Manchester Exeter Liverpool