They wouldn't look favourably at bossman if he started buying tb restricted cows. Bit yes a conversion is achievable relatively cheapWould of thought you could convert existing buildings put in a new 24/48 and buy 250 nice cows (not at @Beef farmer prices, he could do 500 for that budget). Spend a bit on electric fencing, tracks troughs etc. Shouldn't be out of the way to achieve a cfp of £100k+. Not sure what everyone else thinks. Obviously you would need to do a good job at it.
Also you'd only need 250 acres for the above so you'd have plenty of ground left for arable, potato rents, rearing beef calves and young stock or whatever.