The essential part of the HIP, except the energy efficiency report, is already included in a house purchase. Local searches, title plan, etc, are already being paid for in your conveyancing fees under the current system.
Things like the house use form, and list of items included, though required during a typical house purchase, are not currently mandatory in the HIP, but some providers are including them as standard. A basic HIP should not cost any more than about £400 inc VAT. Shop around and u should get it cheaper, especially in the first few months. Some estate agents and solicitors are incorporating the amount into their own fees. Some are simply using a third party HIP provider. U should only be paying £600+ if you live in an 8+ bedroom house, or wish to include things like the Home Condition Report (only useful thing they couldve included as standard for potential purchasers but didnt) and Neighbourhood Report etc. These are all optional extras, and not yet mandatory. Any purchaser will still need to have a survey undertaken, either for their own satisfaction or for lending purposes.
A DIY HIP is an idea, however u would still need to employ a qualified Domestic Energy Assessor to carry out the energy efficiency report, so u may as well just get a provider to do it all for u.
If u refuse to have a HIP done after 1st June, no estate agent should agree to sell your house for u. Its the responsibility of the person (agency) marketing the property to ensure that a HIP is available or else they will get sued. So u would be left trying to sell the property privately. Your purchaser probably wont get a mortgage without one either.
Remember, HIPs have been introduced by the government, most estate agents and conveyancers are against them and dont see them as an aid at all.
Just put your property on the market before the 1st June and avoid it until December!