Your p/e calculations for NBF are wrong because you haven't added back goodwill amortisation which was 2.379 million.....this gives actual diluted earnings of 12.41p per share, or 17.76p per share when taking account of exceptional costs.
That gives a take out figure of 30 x p/e or, less than 20 if ignoring the exceptional items which iirc related to the acquisition of James Budgett Sugars.
Given that the enlarged Company now has a market cap less than NBF, it would take a pretty dire performance from the original RGD business to justify the curent price.
If such a poor performance is already priced in, then one would be entitled to conclude that the shares are at worst fairly rated at the current price.
It doesn't mean that the price won't fall further of course, but then a share price at any given time is not necessarily a fair reflection of that Company's real worth.