Why do you need shorts fella?
In times of budgeting, choose whats needed before luxury.
You can have all the fancy mma shorts in the world - but if you don't know how to kick during sparring then they are worthless, so your shin guards would be a better buy.
140z sparring gloves can be picked up in places such as argos/sports world on the cheap, around £15-£20. choose wisely however (select gloves that have the velcro strapping on them as gloves with lacing can slow up the mma training that can be somewhat fast paced)
Buy Everlast 2314 Pro Style Training Glove - 14oz. at Argos.co.uk - Your Online Shop for .
Decent name aswell - Randy Couture endorses Everlast so you'd impress the ladies...
This gives you £30 to play with...
FIGHTSHOP.COM - Sandee MMA Shin Guard
Some Sandee mma specific shin guards... yes they are £2.99 over your budget but i found alot of companies selling shin guards for as little as £20, just cheaper lesser known brands
Leg & Foot Protection
Blitz sport sell a wide range of shin guards under the £30 mark.
Do you have a mouth guard?
if not i'd buy a mouth guard over shinguards (and just lend someones)
Blitz sport again sell cheap groin guards, cheapest being £6.60
Standard Male Groin Guard
Think in my reckoning this tallies to just over your £50 budget but i'm sure theres some coins hiding in your sofa or in the washing machine to afford the above.