This is available over the counter and has the same active ingredient as adcortyl in orabase.
https://www.superdrug.com/Health/Cough,-Cold-%26-Flu/Cold-Remedies/Difflam-Sore-Throat-Rinse—200ml/p/228202?gclid=Cj0KCQiAzfuNBhCGARIsAD1nu-_jVJfakTsY3EAd0v0mwQOw9XuVEumcaPCI5Z3O59xc_E7Z6Y3bMJwaAmhdEALw_wcB&gclsrc=aw.ds
It’s the most effective thing for numbing sore ulcers, much better than corsodyl, salt or iglu/ bonjela.
Nothing actually heals an ulcer except time and patience. It’s the equivalent of a graze on your skin but the mucosa in the mouth works differently. Ulcers should heal in 1-2 weeks
Some people just “get” ulcers ( recurrent aphthous stomatitis) often stress or hormones can increase their frequency. The majority of the rest are caused by trauma from food or toothbrush. Some viruses cause them also.
There are a number of more unusual things that can cause them. If you get regular ulcers associated with a white patch in the mouth or if you ever have an ulcer that isn’t healing after two weeks, you should get a dentist to check it out. A common presentation of oral cancer is a (often painless ) non healing ulcer.