I am in Scotland and started out around 7 months ago with a similar budget. I have since ended up spending around £2k but my space is much bigger than a wardrobe.
If you are in the Central Belt, stay away from Premier Hydroponics just off the M8 in Edinburgh, the guy is a con merchant!
Much of what you need can be bought from places other than hydro stores.
Charlieshydro ebay store has some decent kit at cheap prices, probably the cheapest online in the UK.
As HL said, lighting, lighting, lighting. Work out the size of your grow area and light it appropriately, a 600w hps is good for around 16 sq ft but they generate a lot of heat, especially in an enclosed space like a wardrobe. You can get a 600W for £70 from CH
Ventilation is the second big element. You will need to exhange the air in your space at least every minute to provide CO2 for the plant(s) and to remove hot air. you can get a 6" fan with a carbon filter for around £90 from CH
Air movement is also a must in an enclosed space to prevent mould and to help strengthen the plant stems. A fan for a wardrobe sized space is less than £20 in Argos.
You will need a ph meter, a hobby style one can be bought for around £25 from ebay. If you go hydro, you will need an EC meter, again for around £25 on ebay.
Genetics, nutrients, containers, etc are all important but the factors above should give you a decent start.
I would suggest getting seeds from an online store, they are secure and safe. Don't use bagseed, it will more than likely hermie on you and you could end up with a ruined crop.
Research is the most important factor though, the more you can learn before starting, the better prepared you will be. I know this sounds obvious but it can never be understated. I did 2 years of reading before commiting to a grow and am still asking questions all the time as new experiences test my very limited skills.
As someone I am deeply indebted to often quotes, you are trying to grow a product that sells for £10 a g in some places in Scotland. Your investment will be repaid.
You are in the best place for help, the guys here really know their stuff and if you invest your time and effort to learn, they will always try to help.
Green mojo my friend.W