hahahahahahahaha be scared, be very scared!!!!
not really! to be honest apart from the core of the video modules - which I sold 3 guitars and a bass to cover (I have more, don't worry) - I've not spent much more than your £300/month budget
you're not really missing anything from the 'big stuff' - it's the support modules that help them play together nicely that are missing
utility modules are the (mostly) inexpensive dull polish that makes the shiny expansive modules actually shine and not tarnish quickly
in your situation I would buy (maybe over time) the 6u rackbrute, maths, a filter that you like, veils - which also has a nice gritty overdrive, btw - an fx aid xl - and a disting mk4* - and then stop and just play with those for a few months
- disting is fantastically useful - it has a lot of uses and can be both a learning tool and a stand in for other modules as required - a lot of people take one look at it and go - "ah a menu, not for me" - a lot of others buy it to try and don't get on with it - mostly because they are constantly fiddling with it to try every algo there is rather than spending some time setting up favourites and have issues reading large manuals - everytime you swap the algo it's like a new module - but a lot of the i/o is similar etc etc - ie the positives far outweigh they negatives, especially in a smaller rack - I will always keep mine - despite to a large extent having physical modules for most of the functions that it provides - I use the tape delay a lot - and some of the functions are in the I just might need that some day category (also one of very few modules with a pitch follower - which is useful if you are using external instruments - as is an envelope follower)
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities