This is actually less true than you think, unless you fire someone for something egregious (Pregnancy, joining a union), they only have a right to challenge whether it was fair if they've been at the company for 2 years. So up until 2 years of employment, whilst there are rules about fair dismissals, the employee can't actually go to a tribunal and enforce those rules, making them basically optional.
To make matters worse, there is a maximum payout anyway, so short of actually writing something totally stupid on the dismisal letter the employer is not going to have many problems.
The maximum amount that you can be awarded as compensation for constructive dismissal is presently the statutory cap of £89,493 or 52 weeks gross salary- whichever is the lower
