Don't do it ....
You sell your 180 for ?1000
You buy a 120 for ?1800 - then spend ?200 on mods you are about ?1000 down.
A 180 does 25 to the gallon
A 120 does 35 to the gallon
10,000 miles is 400 gallons in the 180 - or 285 gallons in the 120
A gallon of fuel at 1.35 a litre is ?6.10 a gallon.
400 gallons at ?6.10 = ?2440
285 gallons at ?6.10 = ?1738
So - in doing 10,000 miles in a 120 instead of a 180 - you will save roughly - ?700 You'll save a bit on tax and a bit on insurance.
Taking into consideration the 180 grin factor - I don't see the value/savings in doing what you are doing if you are going to add money to your car for a 120.
Run what you have got. But hey - just my opinion.
