Is it legal for an employer to let you go after promising you a job and 2 days work?

you have no claim under employement law as you have to be working for 12 months and have an employment contract to claim for unfair/unlawful dismisal but, you may have a claim in the civil court if you want to make a claim in small claims court for the unpaid wages. if you do decide to take this route try to get some documentary evidence that you were promised payment that never materialised.