18,000 is 1325 per month.
Almost anywhere in the country you can rent a room with all bills included for £400 a month, and in many places that will get you a nice double room. In most places you can get a room for much cheaper, but let's assume £400.
A single person can easily feed themselves for £200 a month. Far less honestly, but let's over-budget for the sake of argument.
You mention travel. Perhaps you absolutely have to drive for work (though if you do and are not being paid mileage you are being taken for a ride). It is hard to guess how much you need for this, but for a small cheap car let's say £200 a month for insurance and petrol etc.
Now let's assume a phone contract, a Netflix account and some amount of unnecessary expenditure each month too at £100 so you can see your mates.
This leaves you £425.
Sling £80 per month into a Vanguard account or whatever else you fancy (workplace pension payments etc.).
You can max out the LISA at £333 per month saving you, effectively, £5k per year towards a house. Now, if you are unlucky enough to be on 18k in Oxford or London, for example, then you will be saving like this for a long time admittedly. If you are almost anywhere Birmingham upwards you can buy fairly swiftly with a decently favourable LTV.
If you get a job that requires much less travel or you improve your salary then the rate of savings goes up. Realistically, if you lived very frugally you could save £600+ a month even on your salary assuming you have no large debts you are paying back etc.
Also consider retraining. Do the AAT qualifications in your spare time, become nurse or try to find a way to survive an apprenticeship and become a bricklayer or similar and earn good money.