I agree that you'll struggle at that price. Assuming it's a normal snake, it will be worth around £30-40. You can buy a brand new viv of that size for £60-70. Few people will want the cabinet anyway, so that probably won't add much to the pot. Thermostat £22, ceramic £10, guard £10, fitting £5, light £20.
Even if you pay top dollar, it's difficult to justify more than £200 - and that's with brand new kit.
Draco dormiens nunquam titillandus
“... there is no shame in not knowing. The problem arises when irrational thought and attendant behavior fill the vacuum left by ignorance.”