For a start you haven't added the £935 delivery and £55 first registration fee (£990)!
The price you would pay for a no added option model 3 LR today would be £51990.
Also your claim that it went up £3500 in one hit is simply incorrect!
The price increased by £2000 a couple of days ago, it was previously £49990.
And on October 27th last year the price went up from £48490 to £49990, and increase of £1500.
I recall this very well, because I had ordered my RWD (SR+) the evening before at the old price of £40990.
The following day this went up £1000, and the LR by £1500!