Welcome to the forum, Sagi.
First of all, please remember that only the UK Department for Education can decide whether you will be allowed to teach in England. I suggest you contact them for definitive answers.
As far as I know, you are able to teach in the British state sector only if you have Qualified Teacher Status; I know that CELTA, DELTA and the Trinity Cert and Dip TESOL qualifications do not confer QTS. You will have to find out from the UK Department for Education whether your university Diploma in Teaching English Language and Literature issued confers QTS.
It is up to you whether ot not you continue with your DELTA, but success in it will not give you QTS.
Remember too, that, even if you have/obtain QTS, that is no guarantee of employment. You still have to apply for every teaching job you want - directly to the school concerned, not to any central organisation.